[数据结构与算法]搜索之岛屿的最大面积

每日一题ing，今天是个medium题695. Max Area of Island

class Solution {
public:
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int ret=0;
        for(int i=0;i<grid.size();i++){
            for(int j=0;j<grid[i].size();j++){
                if(grid[i][j]==1)
                ret=max(ret,dfs(grid,i,j));
            }
        }
        return ret;
    }

    int dfs(vector<vector<int>>& grid,int i,int j){
        if(i<0||j<0||i>=grid.size()||j>=grid[i].size()||grid[i][j]==0){
            return 0;
        }

        grid[i][j]=0;//避免重复计算
        int num=1;
        num=num+dfs(grid,i+1,j);
        num=num+dfs(grid,i,j+1);
        num=num+dfs(grid,i-1,j);
        num=num+dfs(grid,i,j-1);
        return num;
    }
};