leetcode 695 经典DFS解法

岛屿的最大面积

class Solution {
public:
    const static int g_dirMaxLen = 4;
    const static int g_dirMaxDim = 2;
    int dir[g_dirMaxLen][g_dirMaxDim] = {
  {-1, 0}, {0, 1}, {1, 0}, {0, -1}};
    int dfs(vector<vector<int>>& grid, int i, int j, int row, int col) {
        if (i < 0 || i >= row || j < 0 || j >= col || grid[i][j] == 0) {
            return 0;
        }
        grid[i][j] = 0;
        int num = 1;
        for (int k = 0; k < g_dirMaxLen; k++) {
            num += dfs(grid, i + dir[k][0], j + dir[k][1], row, col);
        }
        return num;
    }

    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int row = grid.size();
        int col = grid[0].size();
        int res = 0;
        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                if (grid[i][j] == 1) {
                    res = max(res, dfs(grid, i, j, row, col));
                }
            }
        }
        return res;
    }
};