Sloved problem in c++

[Athting]

Solved #51
Problem: 36. Valid Sudoku

// Approach: Hashing with Bitsets

// Implementation Idea

// Use 3 arrays of bitsets (or boolean sets):
// row[9] → track used digits in each row
// col[9] → track used digits in each column
// block[9] → track used digits in each 3×3 block
//
// Traverse the board:
// - Skip if cell is '.'
// - Convert digit '1'–'9' → index 0–8
// - If digit already exists in row/col/block → invalid
// - Else, mark it as used in all three
// If traversal completes with no conflicts → valid board.
// Block index formula: (r / 3) * 3 + (c / 3)

// Intuition

// Think of it as tracking duplicates across three dimensions:
// - Row-wise
// - Column-wise
// - Block-wise

// As we read each cell, we “register” that digit in its row, column, and block.
// If any duplicate appears, it violates Sudoku rules.
// Bitsets make checks and updates O(1) — effectively running 3 hash lookups in parallel.

Complexity

// Time Complexity: O(9×9) = O(1)
// Space Complexity: O(9×3) = O(1)

Code Implementation

class Solution {
public:
bool isValidSudoku(vector<vector>& board) {
vector<bitset<9>> row(9), col(9), block(9);

    for (int r = 0; r < 9; ++r) {
        for (int c = 0; c < 9; ++c) {
            if (board[r][c] == '.') continue;

            int num = board[r][c] - '1';              // convert '1'-'9' → 0-8
            int blockIdx = (r / 3) * 3 + (c / 3);    // find block index

            if (row[r][num] || col[c][num] || block[blockIdx][num])
                return false; // duplicate found

            row[r][num] = col[c][num] = block[blockIdx][num] = 1;
        }
    }
    return true;
}

};

[SjxSubham]

@Athting maintain proper PR description format ...see other closed PR for ref.

the Problem Id.name should be mentioned in the title of the PR... and star the repo as well

[Athting]

@SjxSubham I have updated same pr plz check

[SjxSubham]

@SjxSubham I have updated same pr plz check

fix the file naming format... and remove comments from PR description [Approach, Intuition]... the PR title also should be same as file name