From b62940a75d4cd7a22fc5f7e94bb6dfb7413954a6 Mon Sep 17 00:00:00 2001
From: Ishika Sinha <69107978+ishikasinha-d@users.noreply.github.com>
Date: Mon, 11 Oct 2021 18:29:35 +0530
Subject: [PATCH 1/4] add mountainSubarrayProblem.cpp

---
 Arrays-algos/mountainSubarrayProblem.cpp | 71 ++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 Arrays-algos/mountainSubarrayProblem.cpp

diff --git a/Arrays-algos/mountainSubarrayProblem.cpp b/Arrays-algos/mountainSubarrayProblem.cpp
new file mode 100644
index 0000000..131f86b
--- /dev/null
+++ b/Arrays-algos/mountainSubarrayProblem.cpp
@@ -0,0 +1,71 @@
+// https://practice.geeksforgeeks.org/problems/mountain-subarray-problem/1
+
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution{
+  public:
+    vector<bool> processQueries(int a[], int n, vector<pair<int, int>> &queries,
+                                int q) {
+       
+        vector<bool>ans;
+        int left[n], right[n];
+        left[0]=0;
+        right[n-1]=n-1;
+        int k=0;
+        
+        // left[i] stores the last index on left side which is increasing 
+        // i.e. greater than its previous element
+        for(int i=1; i<n; i++)
+            {
+                if(a[i-1]<a[i])
+                    k=i;
+                left[i]=k;
+            }
+        // right[i] will store the first index on the right side which is decreasing 
+        // i.e. greater than its next element. 
+        for(int i=n-2; i>=0; i--)  
+        {
+            if(a[i+1]<a[i])
+                k=i;
+            right[i]=k;
+            
+        }
+        
+        for(auto x: queries)
+        {
+            int l= x.first;
+            int r= x.second;
+            
+            if(left[r]<=right[l])
+                ans.push_back(true);
+            else
+                ans.push_back(false);
+        }
+    return ans;
+    }
+};
+
+int main() {
+    int tc;
+    cin >> tc;
+    while (tc--) {
+        int n, i, q;
+        cin >> n;
+        int a[n];
+        for (i = 0; i < n; i++) {
+            cin >> a[i];
+        }
+        cin >> q;
+        vector<pair<int, int>> queries(q);
+        for (i = 0; i < q; i++) {
+            cin >> queries[i].first >> queries[i].second;
+        }
+        Solution obj;
+        auto v = obj.processQueries(a, n, queries, q);
+        for (bool u : v) {
+            cout << (u ? "Yes\n" : "No\n");
+        }
+    }
+    return 0;
+} 
\ No newline at end of file

From c2efa3abb04b5a90ecbff2f842f38ae8221299f5 Mon Sep 17 00:00:00 2001
From: Ishika Sinha <69107978+ishikasinha-d@users.noreply.github.com>
Date: Mon, 11 Oct 2021 18:42:51 +0530
Subject: [PATCH 2/4] add mirrorTree.cpp

---
 Binary Tree/mirrorTree.cpp | 123 +++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 Binary Tree/mirrorTree.cpp

diff --git a/Binary Tree/mirrorTree.cpp b/Binary Tree/mirrorTree.cpp
new file mode 100644
index 0000000..67f93d6
--- /dev/null
+++ b/Binary Tree/mirrorTree.cpp	
@@ -0,0 +1,123 @@
+// https://practice.geeksforgeeks.org/problems/mirror-tree/1/?company[]=Google&company[]=Google&page=1&query=company[]Googlepage1company[]Google
+
+#include <bits/stdc++.h>
+using namespace std;
+
+//  A binary tree node has data, pointer to left child and a pointer to right child 
+
+struct Node {
+    int data;
+    struct Node *left;
+    struct Node *right;
+
+    Node(int x) {
+        data = x;
+        left = right = NULL;
+    }
+};
+
+// Function to Build Tree
+Node *buildTree(string str) {
+    // Corner Case
+    if (str.length() == 0 || str[0] == 'N') return NULL;
+
+    // Creating vector of strings from input
+    // string after spliting by space
+    vector<string> ip;
+
+    istringstream iss(str);
+    for (string str; iss >> str;) ip.push_back(str);
+
+    // Create the root of the tree
+    Node *root = new Node(stoi(ip[0]));
+
+    // Push the root to the queue
+    queue<Node *> queue;
+    queue.push(root);
+
+    // Starting from the second element
+    int i = 1;
+    while (!queue.empty() && i < ip.size()) {
+
+        // Get and remove the front of the queue
+        Node *currNode = queue.front();
+        queue.pop();
+
+        // Get the current node's value from the string
+        string currVal = ip[i];
+
+        // If the left child is not null
+        if (currVal != "N") {
+
+            // Create the left child for the current node
+            currNode->left = new Node(stoi(currVal));
+
+            // Push it to the queue
+            queue.push(currNode->left);
+        }
+
+        // For the right child
+        i++;
+        if (i >= ip.size()) break;
+        currVal = ip[i];
+
+        // If the right child is not null
+        if (currVal != "N") {
+
+            // Create the right child for the current node
+            currNode->right = new Node(stoi(currVal));
+
+            // Push it to the queue
+            queue.push(currNode->right);
+        }
+        i++;
+    }
+
+    return root;
+}
+
+/* Helper function to test mirror(). Given a binary
+   search tree, print out its data elements in
+   increasing sorted order.*/
+void inOrder(struct Node *node) {
+    if (node == NULL) return;
+
+    inOrder(node->left);
+    printf("%d ", node->data);
+
+    inOrder(node->right);
+}
+
+class Solution {
+  public:
+    
+    // Function to convert a binary tree into its mirror tree.
+    void mirror(Node* node) {
+        // code here
+        if(node==NULL) return;
+        
+        mirror(node->left);
+        mirror(node->right);
+        
+        //swapping pointers
+        Node* t= node->left;
+        node->left= node->right;
+        node->right= t;
+    }
+};
+
+int main() {
+    int tc;
+    scanf("%d ", &tc);
+    while (tc--) {
+        string str;
+        getline(cin, str);
+        Node *root = buildTree(str);
+        Solution ob;
+        ob.mirror(root);
+        inOrder(root);
+        cout << "\n";
+    }
+
+    return 0;
+}  
\ No newline at end of file

From 5a027feca60888de6a23b019dd66449f9feb3d3d Mon Sep 17 00:00:00 2001
From: Ishika Sinha <69107978+ishikasinha-d@users.noreply.github.com>
Date: Mon, 11 Oct 2021 18:45:27 +0530
Subject: [PATCH 3/4] Delete mirrorTree.cpp

---
 Binary Tree/mirrorTree.cpp | 123 -------------------------------------
 1 file changed, 123 deletions(-)
 delete mode 100644 Binary Tree/mirrorTree.cpp

diff --git a/Binary Tree/mirrorTree.cpp b/Binary Tree/mirrorTree.cpp
deleted file mode 100644
index 67f93d6..0000000
--- a/Binary Tree/mirrorTree.cpp	
+++ /dev/null
@@ -1,123 +0,0 @@
-// https://practice.geeksforgeeks.org/problems/mirror-tree/1/?company[]=Google&company[]=Google&page=1&query=company[]Googlepage1company[]Google
-
-#include <bits/stdc++.h>
-using namespace std;
-
-//  A binary tree node has data, pointer to left child and a pointer to right child 
-
-struct Node {
-    int data;
-    struct Node *left;
-    struct Node *right;
-
-    Node(int x) {
-        data = x;
-        left = right = NULL;
-    }
-};
-
-// Function to Build Tree
-Node *buildTree(string str) {
-    // Corner Case
-    if (str.length() == 0 || str[0] == 'N') return NULL;
-
-    // Creating vector of strings from input
-    // string after spliting by space
-    vector<string> ip;
-
-    istringstream iss(str);
-    for (string str; iss >> str;) ip.push_back(str);
-
-    // Create the root of the tree
-    Node *root = new Node(stoi(ip[0]));
-
-    // Push the root to the queue
-    queue<Node *> queue;
-    queue.push(root);
-
-    // Starting from the second element
-    int i = 1;
-    while (!queue.empty() && i < ip.size()) {
-
-        // Get and remove the front of the queue
-        Node *currNode = queue.front();
-        queue.pop();
-
-        // Get the current node's value from the string
-        string currVal = ip[i];
-
-        // If the left child is not null
-        if (currVal != "N") {
-
-            // Create the left child for the current node
-            currNode->left = new Node(stoi(currVal));
-
-            // Push it to the queue
-            queue.push(currNode->left);
-        }
-
-        // For the right child
-        i++;
-        if (i >= ip.size()) break;
-        currVal = ip[i];
-
-        // If the right child is not null
-        if (currVal != "N") {
-
-            // Create the right child for the current node
-            currNode->right = new Node(stoi(currVal));
-
-            // Push it to the queue
-            queue.push(currNode->right);
-        }
-        i++;
-    }
-
-    return root;
-}
-
-/* Helper function to test mirror(). Given a binary
-   search tree, print out its data elements in
-   increasing sorted order.*/
-void inOrder(struct Node *node) {
-    if (node == NULL) return;
-
-    inOrder(node->left);
-    printf("%d ", node->data);
-
-    inOrder(node->right);
-}
-
-class Solution {
-  public:
-    
-    // Function to convert a binary tree into its mirror tree.
-    void mirror(Node* node) {
-        // code here
-        if(node==NULL) return;
-        
-        mirror(node->left);
-        mirror(node->right);
-        
-        //swapping pointers
-        Node* t= node->left;
-        node->left= node->right;
-        node->right= t;
-    }
-};
-
-int main() {
-    int tc;
-    scanf("%d ", &tc);
-    while (tc--) {
-        string str;
-        getline(cin, str);
-        Node *root = buildTree(str);
-        Solution ob;
-        ob.mirror(root);
-        inOrder(root);
-        cout << "\n";
-    }
-
-    return 0;
-}  
\ No newline at end of file

From 0d721ecb73e874822ca11b57b33fa617af37ae5e Mon Sep 17 00:00:00 2001
From: Ishika Sinha <69107978+ishikasinha-d@users.noreply.github.com>
Date: Mon, 11 Oct 2021 18:59:58 +0530
Subject: [PATCH 4/4] Create sortByFrequency.cpp

---
 Hashing/sortByFrequency.cpp | 77 +++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 Hashing/sortByFrequency.cpp

diff --git a/Hashing/sortByFrequency.cpp b/Hashing/sortByFrequency.cpp
new file mode 100644
index 0000000..2906bdb
--- /dev/null
+++ b/Hashing/sortByFrequency.cpp
@@ -0,0 +1,77 @@
+//https://practice.geeksforgeeks.org/problems/sorting-elements-of-an-array-by-frequency-1587115621/1/
+// Sorting Elements of an Array by Frequency 
+
+#include<bits/stdc++.h>
+using namespace std;
+
+class Solution{
+    public:
+    
+    static bool cmp( pair<int, int> &a, pair<int, int> &b)
+    {
+        if(a.second==b.second)
+            return a.first<b.first;
+        return a.second>b.second;
+    }
+   
+    vector<int> sortByFreq(int arr[],int n)
+    {
+        //Your code here
+        vector<int>ans;
+        map<int,int> m;
+        vector<pair<int, int> > A;
+        
+        for(int i=0; i<n; i++)
+        {
+            int x= arr[i];
+            m[x]++;
+        }
+        // Copy key-value pair from Map
+        // to vector of pairs
+        for (auto &it : m) {
+            A.push_back(it);
+        }
+        sort(A.begin(), A.end(), cmp) ;
+        
+        for(auto x: A)
+        {
+           while(x.second)
+           {
+               ans.push_back(x.first);
+               x.second--;
+           }
+            
+        }   
+        
+        return ans;
+    }
+};
+
+int main() {
+	
+	
+	int t;
+	cin >> t;
+	
+	
+	while(t--){
+	    
+	    
+	    int n;
+	    cin >> n;
+	    
+	    int a[n+1];
+	    
+	    for(int i = 0;i<n;i++){
+	        cin >> a[i];
+	    }
+	    Solution obj;
+	    vector<int> v;
+	    v = obj.sortByFreq(a,n);
+	    for(int i:v)
+	        cout<<i<<" ";
+	    cout << endl;
+	}
+	
+	return 0;
+}