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'
.
Rust Solution
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);
}
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