Lonely pixel i

Array Hash Table Matrix

62.7% acceptance

Mar 31, 2026

451

Given an m x n picture consisting of black 'B' and white 'W' pixels, return the number of black lonely pixels. A black lonely pixel is a character 'B' that located at a specific position where the same row and same column don't have any other black pixels.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn find_lonely_pixel(picture: Vec<Vec<char>>) -> i32 {
    let m = picture.len();
    let n = picture[0].len();
    let mut row_count = vec![0; m];
    let mut col_count = vec![0; n];
    for i in 0..m {
      for j in 0..n {
        if picture[i][j] == 'B' {
          row_count[i] += 1;
          col_count[j] += 1;
        }
      }
    }
    let mut count = 0;
    for i in 0..m {
      for j in 0..n {
        if picture[i][j] == 'B' && row_count[i] == 1 && col_count[j] == 1 {
          count += 1;
        }
      }
    }
    count
  }
}