36. Valid Sudoku / Medium / JavaScript

yeongrok/0036-valid-sudoku/0036-valid-sudoku.js

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+/**
+ * @param {character[][]} board
+ * @return {boolean}
+ */
+var isValidSudoku = function(board) {
+    /* 0 1 2
+       3 4 5
+       6 7 8 */
+    const area = [...Array(10).keys()].map(i => ({}));
+
+    const columns = [...Array(10).keys()].map(i => ({}));
+
+    for (let i = 0; i < board.length; i++) {
+        const row = board[i];
+        const appearedInRow = {};
+        for (let j = 0; j < row.length; j++) {
+            if (row[j] !== "." && (row[j] < 1 || row[j] > 9 || appearedInRow[row[j]] || columns[j][row[j]])) return false;
+            appearedInRow[row[j]] = true;
+            columns[j][row[j]] = true;
+
+            let areaNum;
+            if (i < 3) {
+                if (j < 3) {
+                    areaNum = 0;
+                } else if (j < 6) {
+                    areaNum = 1;                    
+                } else {
+                    areaNum = 2;
+                }
+            } else if (i < 6) {
+                if (j < 3) {
+                    areaNum = 3;
+                } else if (j < 6) {
+                    areaNum = 4;
+                } else {
+                    areaNum = 5;
+                }
+            }
+            else {
+                if (j < 3) {
+                    areaNum = 6;
+                } else if (j < 6) {
+                    areaNum = 7;
+                } else {
+                    areaNum = 8;
+                }
+
+            }
+            if (row[j] !== "." && area[areaNum][row[j]]) return false;
+            area[areaNum][row[j]] = true;
+        }
+    }
+    return true;
+};

yeongrok/0036-valid-sudoku/README.md

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+<h2><a href="https://leetcode.com/problems/valid-sudoku/">36. Valid Sudoku</a></h2><h3>Medium</h3><hr>Can you solve this real interview question? Valid Sudoku - Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
+
+ 1. Each row must contain the digits 1-9 without repetition.
+ 2. Each column must contain the digits 1-9 without repetition.
+ 3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.
+
+Note:
+
+ * A Sudoku board (partially filled) could be valid but is not necessarily solvable.
+ * Only the filled cells need to be validated according to the mentioned rules.
+
+
+
+Example 1:
+
+[https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Sudoku-by-L2G-20050714.svg/250px-Sudoku-by-L2G-20050714.svg.png]
+
+
+Input: board = 
+[["5","3",".",".","7",".",".",".","."]
+,["6",".",".","1","9","5",".",".","."]
+,[".","9","8",".",".",".",".","6","."]
+,["8",".",".",".","6",".",".",".","3"]
+,["4",".",".","8",".","3",".",".","1"]
+,["7",".",".",".","2",".",".",".","6"]
+,[".","6",".",".",".",".","2","8","."]
+,[".",".",".","4","1","9",".",".","5"]
+,[".",".",".",".","8",".",".","7","9"]]
+Output: true
+
+
+Example 2:
+
+
+Input: board = 
+[["8","3",".",".","7",".",".",".","."]
+,["6",".",".","1","9","5",".",".","."]
+,[".","9","8",".",".",".",".","6","."]
+,["8",".",".",".","6",".",".",".","3"]
+,["4",".",".","8",".","3",".",".","1"]
+,["7",".",".",".","2",".",".",".","6"]
+,[".","6",".",".",".",".","2","8","."]
+,[".",".",".","4","1","9",".",".","5"]
+,[".",".",".",".","8",".",".","7","9"]]
+Output: false
+Explanation: Same as Example 1, except with the 5 in the top left corner being modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
+
+
+
+
+Constraints:
+
+ * board.length == 9
+ * board[i].length == 9
+ * board[i][j] is a digit 1-9 or '.'.