531.cpp

class Solution {
public:
    int findLonelyPixel(vector<vector<char>>& picture) {
        int m = picture.size();
        int n = picture[0].size();
        
        vector<int> rows(m, 0);
        vector<int> cols(n, 0);
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (picture[i][j] == 'B') {
                    rows[i]++;
                    cols[j]++;
                }
            }
        }
        
        int cnt = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (picture[i][j] == 'B') {
                    if (rows[i] == 1 && cols[j] == 1) cnt++;
                }
            }
        }
        return cnt;
    }
};