class Solution {
public:
    int trap(vector<int>& height) {
        pair<int,int> que;
        int len = height.size();
        if(len<3) return 0;
        int res = 0;
        que.first = 0;
        que.second = len-1;
        int Max = -1;
        while(que.first<que.second)
        {
            //Max = max(height[que.first],height[que.second]);
            if(height[que.first]<=height[que.second])
            {
                if(height[que.first]>Max) Max = height[que.first];
                if(Max>height[que.first+1]) res+=Max - height[que.first+1];
                que.first++;
            }
            else
            {
                if(Max<height[que.second]) Max = height[que.second];
                if(Max>height[que.second-1]) res+= Max-height[que.second-1];
                que.second--;
            }
            
        }
        return res;
    }
};

class Solution {
public:
    int trapRainWater(vector<vector<int>>& heightMap) {
        
        int res = 0;
        
        int m = heightMap.size();
        if(m==0) return 0;
        int n = heightMap[0].size();
        priority_queue < pair<int,pair<int,int>>,vector<pair<int,pair<int,int>>>,greater< pair<int,pair<int,int>> > > que;
        
        vector<vector<int> > visited(m,vector<int>(n,0));
        
        int dir[] = {0,1,0,-1,0};
        
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(!(i==0||i==m-1||j==0||j==n-1)) continue;
                que.push(make_pair(heightMap[i][j],make_pair(i,j)));
                visited[i][j] = 1;
                
            }
        }

        int MAX = -10;
        while(!que.empty())
        {
            pair<int,pair<int,int>> temp = que.top();que.pop();
            if(temp.first>MAX) MAX = temp.first;
            
            int x = temp.second.first;
            int y = temp.second.second;
            
            
            
            for(int i=0;i<4;i++)
            {
                int a = x+dir[i];
                int b = y+dir[i+1];
                
                if(a>=0&&a<m&&b>=0&&b<n&&visited[a][b]==0)
                {
                    que.push(make_pair(heightMap[a][b],make_pair(a,b)));
                    if(MAX > heightMap[a][b])  res += MAX - heightMap[a][b];
                    visited[a][b] = 1;
                }
            }
        }
        return res;
    }
};