题目：

题解：

const int dx[4] = {0, 1, 0, -1};
const int dy[4] = {1, 0, -1, 0};int dfs(int x, int y, int** grid, int n, int m) {if (x < 0 || x >= n || y < 0 || y >= m || grid[x][y] == 0) {return 1;}if (grid[x][y] == 2) {return 0;}grid[x][y] = 2;int res = 0;for (int i = 0; i < 4; ++i) {int tx = x + dx[i];int ty = y + dy[i];res += dfs(tx, ty, grid, n, m);}return res;
}int islandPerimeter(int** grid, int gridSize, int* gridColSize) {int n = gridSize, m = gridColSize[0];int ans = 0;for (int i = 0; i < n; ++i) {for (int j = 0; j < m; ++j) {if (grid[i][j] == 1) {ans += dfs(i, j, grid, n, m);}}}return ans;
}