Valid Sudoku LeetCode Programming Solutions | LeetCode Problem Solutions in C++, Java, & Python [💯Correct]

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Hello Programmers/Coders, Today we are going to share solutions to the Programming problems of LeetCode Solutions in C++, Java, & Python. At Each Problem with Successful submission with all Test Cases Passed, you will get a score or marks and LeetCode Coins. And after solving maximum problems, you will be getting stars. This will highlight your profile to the recruiters.

In this post, you will find the solution for the Valid Sudoku in C++, Java & Python-LeetCode problem. We are providing the correct and tested solutions to coding problems present on LeetCode. If you are not able to solve any problem, then you can take help from our Blog/website.

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About LeetCode

LeetCode is one of the most well-known online judge platforms to help you enhance your skills, expand your knowledge and prepare for technical interviews. 

LeetCode is for software engineers who are looking to practice technical questions and advance their skills. Mastering the questions in each level on LeetCode is a good way to prepare for technical interviews and keep your skills sharp. They also have a repository of solutions with the reasoning behind each step.

LeetCode has over 1,900 questions for you to practice, covering many different programming concepts. Every coding problem has a classification of either EasyMedium, or Hard.

LeetCode problems focus on algorithms and data structures. Here is some topic you can find problems on LeetCode:

  • Mathematics/Basic Logical Based Questions
  • Arrays
  • Strings
  • Hash Table
  • Dynamic Programming
  • Stack & Queue
  • Trees & Graphs
  • Greedy Algorithms
  • Breadth-First Search
  • Depth-First Search
  • Sorting & Searching
  • BST (Binary Search Tree)
  • Database
  • Linked List
  • Recursion, etc.

Leetcode has a huge number of test cases and questions from interviews too like Google, Amazon, Microsoft, Facebook, Adobe, Oracle, Linkedin, Goldman Sachs, etc. LeetCode helps you in getting a job in Top MNCs. To crack FAANG Companies, LeetCode problems can help you in building your logic.

Link for the ProblemValid Sudoku– LeetCode Problem

Valid Sudoku– LeetCode Problem


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.


  • 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:

250px Sudoku by L2G 20050714.svg
Input: board = 
Output: true

Example 2:

Input: board = 
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.


  • board.length == 9
  • board[i].length == 9
  • board[i][j] is a digit 1-9 or '.'.
Valid Sudoku– LeetCode Solutions
class Solution {
  bool isValidSudoku(vector<vector<char>>& board) {
    unordered_set<string> seen;

    for (int i = 0; i < 9; ++i)
      for (int j = 0; j < 9; ++j) {
        if (board[i][j] == '.')
        const string c(1, board[i][j]);
        if (!seen.insert(c + "@row" + to_string(i)).second ||
            !seen.insert(c + "@col" + to_string(j)).second ||
            !seen.insert(c + "@box" + to_string(i / 3) + to_string(j / 3))
          return false;

    return true;
class Solution {
  public boolean isValidSudoku(char[][] board) {
    Set<String> seen = new HashSet<>();

    for (int i = 0; i < 9; ++i)
      for (int j = 0; j < 9; ++j) {
        if (board[i][j] == '.')
        final char c = board[i][j];
        if (!seen.add(c + "@row" + i) ||
            !seen.add(c + "@col" + j) ||
            !seen.add(c + "@box" + i / 3 + j / 3))
          return false;

    return true;
class Solution:
  def isValidSudoku(self, board: List[List[str]]) -> bool:
    seen = set()

    for i in range(9):
      for j in range(9):
        c = board[i][j]
        if c == '.':
        if c + '@row ' + str(i) in seen or \
           c + '@col ' + str(j) in seen or \
           c + '@box ' + str(i // 3) + str(j // 3) in seen:
          return False
        seen.add(c + '@row ' + str(i))
        seen.add(c + '@col ' + str(j))
        seen.add(c + '@box ' + str(i // 3) + str(j // 3))

    return True

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