Valid sudoku

Array Hash Table Matrix

64.2% acceptance

Jan 12, 2026

12400

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Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each row must contain the digits 1-9 without repetition. Each column must contain the digits 1-9 without repetition. 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.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn is_valid_sudoku(board: Vec<Vec<char>>) -> bool {
    use std::collections::HashSet;
    
    let mut rows: Vec<HashSet<char>> = vec![HashSet::new(); 9];
    let mut cols: Vec<HashSet<char>> = vec![HashSet::new(); 9];
    let mut boxes: Vec<HashSet<char>> = vec![HashSet::new(); 9];
    
    for i in 0..9 {
      for j in 0..9 {
        let c = board[i][j];
        if c == '.' {
          continue;
        }
        
        // Check row
        if rows[i].contains(&c) {
          return false;
        }
        rows[i].insert(c);
        
        // Check column
        if cols[j].contains(&c) {
          return false;
        }
        cols[j].insert(c);
        
        // Check 3x3 box
        let box_index = (i / 3) * 3 + (j / 3);
        if boxes[box_index].contains(&c) {
          return false;
        }
        boxes[box_index].insert(c);
      }
    }
    
    true
  }
}