1003. 相连的1

对于一个01矩阵A，求其中有多少片连成一片的1. 每个1可以和上下左右的1相连.

思路：泛洪(DFS)

class Solution {public:    void flood(vector<vector<char>>& A, int i, int j, int m, int n) {        if (i < m && i >= 0 && j < n && j >= 0 && A[i][j] == '1') {            A[i][j] = '0';            flood(A, i-1, j, m, n);            flood(A, i+1, j, m, n);            flood(A, i, j-1, m, n);            flood(A, i, j+1, m, n);        }    }    int countConnectedOnes(vector<vector<char>>& A) {        int m = A.size();        if (m == 0) return 0;        int n = A[0].size();        if (n == 0) return 0;        int count = 0;        for (int i = 0; i < m; i++)            for (int j = 0; j < n; j++)                if (A[i][j] == '1') {                    count++;                    flood(A, i, j, m, n);                }        return count;    }};