Here, We see Valid Sudoku LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

List of all LeetCode Solution

Valid Sudoku LeetCode Solution

Problem Statement

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.

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.

Valid Sudoku Leetcode Solution C++

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        int row[9][9] = {0}, col[9][9] = {0}, grid_3x3[9][9] = {0}; 
        
        for(int i = 0; i < board.size(); i++)
            for(int j = 0; j < board[i].size(); j++)
                if(board[i][j] != '.')
                {
                    int num = board[i][j] - '1', k = i/3*3+j/3; //k for finding grid index from 0 to 8
                    if(row[i][num] || col[j][num] || grid_3x3[k][num])
                        return false;
                    row[i][num] = col[j][num] = grid_3x3[k][num] = 1;
                }
        
        return true;        
    }
};Code language: PHP (php)

Valid Sudoku Leetcode Solution Java

class Solution {
    public boolean isValidSudoku(char[][] board) {
    for(int i = 0; i<9; i++){
        HashSet<Character> rows = new HashSet<Character>();
        HashSet<Character> columns = new HashSet<Character>();
        HashSet<Character> cube = new HashSet<Character>();
        for (int j = 0; j < 9;j++){
            if(board[i][j]!='.' && !rows.add(board[i][j]))
                return false;
            if(board[j][i]!='.' && !columns.add(board[j][i]))
                return false;
            int RowIndex = 3*(i/3);
            int ColIndex = 3*(i%3);
            if(board[RowIndex + j/3][ColIndex + j%3]!='.' && !cube.add(board[RowIndex + j/3][ColIndex + j%3]))
                return false;
        }
    }
    return true;    
    }
}Code language: PHP (php)

Valid Sudoku Leetcode Solution JavaScript

var isValidSudoku = function(board) {
  let rows = new Set();
  let cols = new Set();
  let boxes = new Set();
  let curRowElem;
  let curColElem;
  let curBoxElem;

  for (let i = 0; i < board.length; i += 1) {
    for (let j = 0; j < board[0].length; j += 1) {
      curRowElem = board[i][j]
      curColElem = board[j][i]
      curBoxElem = board[3 * Math.floor(i / 3) + Math.floor(j / 3)][((i * 3) % 9) + (j % 3)]

      if (rows.has(curRowElem)) return false;
      if (curRowElem !== ".") rows.add(curRowElem);

      if (cols.has(curColElem)) return false;
      if (curColElem !== ".") cols.add(curColElem);

      if (boxes.has(curBoxElem)) return false;
      if (curBoxElem !== ".") boxes.add(curBoxElem);
    }

    rows.clear()
    cols.clear()
    boxes.clear()
  }

  return true;  
};Code language: JavaScript (javascript)

Valid Sudoku Leetcode Solution Python

class Solution(object):
    def isValidSudoku(self, board):
        big = set()
        for i in xrange(0,9):
            for j in xrange(0,9):
                if board[i][j]!='.':
                    cur = board[i][j]
                    if (i,cur) in big or (cur,j) in big or (i/3,j/3,cur) in big:
                        return False
                    big.add((i,cur))
                    big.add((cur,j))
                    big.add((i/3,j/3,cur))
        return True