【LeetCode】Number of Islands 解题报告

public int numIslands(char[][] grid) {
m = grid.length;
if (m == 0) return 0;
n = grid[0].length;
if (n == 0) return 0;

int ans = 0;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (grid[i][j] != '1') continue;

ans++;
dfs(grid, i, j);
}
}
return ans;
}

public void dfs(char[][] grid, int i, int j) {
if (i < 0 || i >= m || j < 0 || j >= n) return;

if (grid[i][j] == '1') {
grid[i][j] = '2';
dfs(grid, i – 1, j);
dfs(grid, i + 1, j);
dfs(grid, i, j – 1);
dfs(grid, i, j + 1);
}
}
}