778-1

class Solution {

struct node{
    int x, y, t;
    node(int x, int y, int t): x(x), y(y), t(t){}
    bool operator<(const node &tmp) const{
        return t > tmp.t;
    }
};

public:
    int swimInWater(vector<vector<int>>& grid) {
        int ans = 0, rows = grid.size(), cols = grid[0].size();
        int d[4][2] = {{1,0},{-1,0},{0,1},{0,-1}};
        bool vis[rows][cols];
        memset(vis, 0, sizeof vis);

        priority_queue<node> q;
        q.push(node(0, 0, grid[0][0]));
        vis[0][0] = true;

        while(!q.empty()){
            node curr = q.top();
            q.pop();
            ans = max(ans, curr.t);
            if(curr.x == rows-1 && curr.y == cols-1)
                return ans;
            for(int i=0; i<4; i++){
                int nextX = curr.x+d[i][0], nextY = curr.y+d[i][1];
                if(nextX < 0 || nextX >= rows || nextY < 0 || nextY >= cols || vis[nextX][nextY])
                    continue;
                node next = node(nextX, nextY, grid[nextX][nextY]);
                q.push(next);
                vis[nextX][nextY] = true;
            }
        }
        return ans;
    }
};