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'time complexity and big O'
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‎10.Python Code Challenges/04_GettingReady_Time_Complexity_Big O/Sample Question 4 - 2D Array and Time Complexity.ipynb

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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Problem: Counting the number of negative numbers.\n",
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"\n",
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"You are given a 2-dimensional array with integers.\n",
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"\n",
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"Example Input: \n",
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"[[-4, -3, -1, 1], \n",
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" [-2, -2, 1, 2], \n",
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" [-1,  1,  2, 3], \n",
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" [ 1,  2,  4, 5]]\n",
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"\n",
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"Write a function, count_negatives(input), which finds and returns the number of negative integers in th array."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### NOTE: Make sure to run your program once you write it :)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Implement your function below."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {},
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"outputs": [],
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"source": [
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"# Input: A 2-dimensional array with integers. Example below.\n",
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"#[[-4, -3, -1, 1],\n",
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"# [-2, -2, 1, 2],\n",
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"# [-1, 1, 2, 3],\n",
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"# [ 1, 2, 4, 5]]\n",
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"# Returns:\n",
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"# The number of negative numbers in the array.\n",
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"# In the above case, this function should return 6\n",
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"# since there are 6 negative numbers in the array.\n",
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"def count_negatives(given_array):\n",
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" count = 0\n",
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" row_i = 0\n",
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" col_i = len(given_array) - 1 # start from the right most last columns and move to left\n",
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" \n",
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" while col_i >= 0 and row_i < len(given_array):\n",
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" if given_array[row_i][col_i] < 0:\n",
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" count += (col_i + 1)\n",
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" row_i += 1\n",
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" else:\n",
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" col_i -= 1 # move to left side\n",
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"\n",
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" return count"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Use the code below to test your function."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"\n",
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"How many negative numbers are there in the following array?\n",
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"(There are 6.)\n",
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"\n",
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"[[-4, -3, -1, 1],\n",
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" [-2, -2, 1, 2],\n",
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" [-1, 1, 2, 3],\n",
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" [ 1, 2, 4, 5]]\n",
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"\n"
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]
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},
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{
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"data": {
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"text/plain": [
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"6"
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]
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},
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"execution_count": 2,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"print(\"\"\"\n",
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"How many negative numbers are there in the following array?\n",
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"(There are 6.)\n",
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"\n",
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"[[-4, -3, -1, 1],\n",
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" [-2, -2, 1, 2],\n",
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" [-1, 1, 2, 3],\n",
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" [ 1, 2, 4, 5]]\n",
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"\"\"\")\n",
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"\n",
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"count_negatives(\n",
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"[[-4, -3, -1, 1],\n",
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" [-2, -2, 1, 2],\n",
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" [-1, 1, 2, 3],\n",
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" [ 1, 2, 4, 5]])"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"\n",
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"How many negative numbers are there in the following array?\n",
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"(There is 1.)\n",
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"\n",
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"[[-1, 0],\n",
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" [0, 0]]\n",
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"\n"
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]
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},
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{
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"data": {
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"text/plain": [
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"1"
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]
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},
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"execution_count": 3,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"print(\"\"\"\n",
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"How many negative numbers are there in the following array?\n",
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"(There is 1.)\n",
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"\n",
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"[[-1, 0],\n",
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" [0, 0]]\n",
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"\"\"\")\n",
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"\n",
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"count_negatives(\n",
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"[[-1, 0],\n",
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" [0, 0]])"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"\n",
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"How many negative numbers are there in the following array?\n",
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"(There are 2.)\n",
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"\n",
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"[[-2, 0],\n",
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" [-1, 0]]\n",
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"\n"
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]
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},
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{
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"data": {
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"text/plain": [
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"2"
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]
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},
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"execution_count": 4,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"print(\"\"\"\n",
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"How many negative numbers are there in the following array?\n",
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"(There are 2.)\n",
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"\n",
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"[[-2, 0],\n",
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" [-1, 0]]\n",
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"\"\"\")\n",
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"\n",
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"count_negatives(\n",
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"[[-2, 0],\n",
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" [-1, 0]])"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 5,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"\n",
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"How many negative numbers are there in the following array?\n",
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"(There are none.)\n",
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"\n",
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"[[0]]\n",
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"\n"
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]
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},
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{
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"data": {
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"text/plain": [
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"0"
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]
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},
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"execution_count": 5,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"print(\"\"\"\n",
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"How many negative numbers are there in the following array?\n",
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"(There are none.)\n",
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"\n",
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"[[0]]\n",
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"\"\"\")\n",
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"\n",
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"count_negatives([[0]])"
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]
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}
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],
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"metadata": {
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"anaconda-cloud": {},
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.7.6"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 1
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}

‎10.Python Code Challenges/04_GettingReady_Time_Complexity_Big O/negative_counter_with_BigO(n).py

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# Problem: Counting the number of negative numbers.
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# You are given a 2-dimensional array with integers.
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# Example Input:
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# [[-4, -3, -1, 1],
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# [-2, -2, 1, 2],
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# [-1, 1, 2, 3],
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# [ 1, 2, 4, 5]]
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# Write a function, count_negatives(input), which finds and returns the number of negative integers in th array.
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# Input: A 2-dimensional array with integers. Example below.
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#[[-4, -3, -1, 1],
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# [-2, -2, 1, 2],
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# [-1, 1, 2, 3],
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# [ 1, 2, 4, 5]]
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# Returns:
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# The number of negative numbers in the array.
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# In the above case, this function should return 6
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# since there are 6 negative numbers in the array.
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def count_negatives(given_array):
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count = 0
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row_i = 0
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col_i = len(given_array) - 1 # start from the right most last columns and move to left
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while col_i >= 0 and row_i < len(given_array):
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if given_array[row_i][col_i] < 0:
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count += (col_i + 1)
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row_i += 1
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else:
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col_i -= 1 # move to left side
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return count
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if __name__ == "__main__":
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print("""
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How many negative numbers are there in the following array?
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(There are 6.)
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[[-4, -3, -1, 1],
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[-2, -2, 1, 2],
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[-1, 1, 2, 3],
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[ 1, 2, 4, 5]]
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""")
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result = count_negatives(
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[[-4, -3, -1, 1],
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[-2, -2, 1, 2],
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[-1, 1, 2, 3],
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[ 1, 2, 4, 5]])
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print(result)
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print("""
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How many negative numbers are there in the following array?
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(There is 1.)
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[[-1, 0],
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[0, 0]]
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""")
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result = count_negatives(
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[[-1, 0],
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[0, 0]])
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print(result)
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print("""
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How many negative numbers are there in the following array?
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(There are 2.)
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[[-2, 0],
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[-1, 0]]
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""")
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result = count_negatives(
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[[-2, 0],
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[-1, 0]])
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print(result)
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print("""
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How many negative numbers are there in the following array?
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(There are none.)
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[[0]]
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""")
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result = count_negatives([[0]])
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print(result)

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