200. 岛屿数量
dfs
四个方向dfs就行了，走过的地方标0
#include <iostream>
#include <vector>
using namespace std;
class Solution {
public:
void dfs(int i, int j, vector<vector<char>> &grid) {
if (i < 0 || j < 0 || i >= grid.size() || j >= grid[i].size() ||
grid[i][j] == '0')
return;
grid[i][j] = '0';
dfs(i + 1, j, grid);
dfs(i, j - 1, grid);
dfs(i - 1, j, grid);
dfs(i, j + 1, grid);
}
int numIslands(vector<vector<char>> &grid) {
int cnt = 0;
for (int i = 0; i < grid.size(); i++) {
for (int j = 0; j < grid[i].size(); j++) {
if (grid[i][j] == '1') {
cnt++;
dfs(i, j, grid);
}
}
}
return cnt;
}
};
int main() {
Solution s;
vector<vector<char>> grid = {{'1', '0', '1', '1', '1'},
{'1', '0', '1', '0', '1'},
{'1', '1', '1', '0', '1'}};
int res = s.numIslands(grid);
cout << res;
return 0;
}
