Max Area of Island（C++岛屿的最大面积）-蒲公英云

Max Area of Island（C++岛屿的最大面积）

解题思路：

（1）利用栈(stack)来进行深度遍历(dfs)

class Solution {
public:
    void helper(vector<int> &v,vector<vector<int>> &d,vector<int> &vis,vector<vector<int>>& grid,
                stack<pair<int,int>> &s,int x,int y,int m,int n,int &sum) {
        sum += grid[x][y];
        vis[x*n+y] = 1;
        for(int i=0;i<d.size();i++) {
            if(0<=x+d[i][0] && x+d[i][0]<m && 0<=y+d[i][1] && 
               y+d[i][1]<n && grid[x+d[i][0]][y+d[i][1]]==1 && vis[(x+d[i][0])*n+y+d[i][1]]==0) {
                s.push(pair(x+d[i][0],y+d[i][1]));
            } 
        }
        while(!s.empty()) {
            auto temp = s.top();
            s.pop();
            if(vis[temp.first*n+temp.second]==0)
                helper(v,d,vis,grid,s,temp.first,temp.second,m,n,sum);
        }
        v.push_back(sum);
        return;
    }
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int m = grid.size(),n=grid[0].size();
        vector<int> v;
        vector<int> vis(m*n,0);
        vector<vector<int>> d={
   {1,0},{-1,0},{0,1},{0,-1}};
        int sum = 0;
        for(int i=0;i<grid.size();i++) {
            for(int j=0;j<grid[i].size();j++) {
                sum=0;
                if(grid[i][j]==1) {
                    stack<pair<int,int>> s;
                    helper(v,d,vis,grid,s,i,j,m,n,sum);
                } else v.push_back(sum);
            }
        }
        auto max_index = max_element(v.begin(),v.end())-v.begin();
        return v[max_index];
    }
};