每日一题 407. 接雨水 II

407. 接雨水 II

使用优先队列

class Solution {
public:
    int trapRainWater(vector<vector<int>>& heightMap) {


        int water = 0;
        priority_queue<vector<int>,vector<vector<int>>,greater<vector<int>>> que;
        
        int m = heightMap.size();
        int n = heightMap[0].size();
        vector<vector<int>> visited(m,vector<int>(n,false));
        for(int i=0;i<m;++i)
        {
            que.push({heightMap[i][0],i,0});
            que.push({heightMap[i][n-1],i,n-1});
            visited[i][0] = true;
            visited[i][n-1] = true;
        }
        for(int j=1;j<n-1;++j)
        {
            que.push({heightMap[0][j],0,j});
            que.push({heightMap[m-1][j],m-1,j});
            visited[0][j] = true;
            visited[m-1][j] = true;
        }
        int dx[4] = {1,0,-1,0};
        int dy[4] = {0,1,0,-1};
        
        while(!que.empty())
        {
            auto t = que.top();
            que.pop();
            int curH = t[0];
            int x    = t[1];
            int y    = t[2];
            for(int i=0;i<4;++i)
            {
                int nx = dx[i] + x;
                int ny = dy[i] + y;
                if(nx>=0 && nx < m && ny >= 0 && ny < n && !visited[nx][ny])
                {
                    
                    water += max(0,curH - heightMap[nx][ny]);
                    visited[nx][ny] = true;
                    que.push({max(curH,heightMap[nx][ny]),nx,ny});
                }
            }

        }

        return water;
    }
};