531. Lonely Pixel I

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.

Example 1:

```Input: picture = [["W","W","B"],["W","B","W"],["B","W","W"]]
Output: 3
Explanation: All the three 'B's are black lonely pixels.
```

Example 2:

```Input: picture = [["B","B","B"],["B","B","B"],["B","B","B"]]
Output: 0
```

Constraints:

• `m == picture.length`
• `n == picture[i].length`
• `1 <= m, n <= 500`
• `picture[i][j]` is `'W'` or `'B'`.

531. Lonely Pixel I
``````struct Solution;

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

#[test]
fn test() {
let pictures = vec_vec_char![['W', 'W', 'B'], ['W', 'B', 'W'], ['B', 'W', 'W']];
let res = 3;
assert_eq!(Solution::find_lonely_pixel(pictures), res);
}
``````