1102. Path With Maximum Minimum Value

Given a matrix of integers A with R rows and C columns, find the maximum score of a path starting at [0,0] and ending at [R-1,C-1].

The score of a path is the minimum value in that path.  For example, the value of the path 8 →  4 →  5 →  9 is 4.

A path moves some number of times from one visited cell to any neighbouring unvisited cell in one of the 4 cardinal directions (north, east, west, south).

 

Example 1:

Input: [[5,4,5],[1,2,6],[7,4,6]]
Output: 4
Explanation: 
The path with the maximum score is highlighted in yellow. 

Example 2:

Input: [[2,2,1,2,2,2],[1,2,2,2,1,2]]
Output: 2

Example 3:

Input: [[3,4,6,3,4],[0,2,1,1,7],[8,8,3,2,7],[3,2,4,9,8],[4,1,2,0,0],[4,6,5,4,3]]
Output: 3

class Solution {
    public int maximumMinimumPath(int[][] A) {
        int[][] DIRS = { { 0, 1 }, { 1, 0 }, { 0, -1 }, { -1, 0 } };
        int n = A.length, m = A[0].length;
        Queue<int[]> pq = new PriorityQueue<>((a, b) -> Integer.compare(b[0], a[0]));
        pq.offer(new int[] { A[0][0], 0, 0 });
        int maxscore = A[0][0];
        A[0][0] = -1; // visited
        while (!pq.isEmpty()) {
            int[] top = pq.poll();
            maxscore = Math.min(maxscore, top[0]);
            if (top[1] == n - 1 && top[2] == m - 1)
                break;
            for (int[] d : DIRS) {
                int newi = d[0] + top[1], newj = d[1] + top[2];
                if (newi >= 0 && newi < n && newj >= 0 && newj < m && A[newi][newj] >= 0) {
                    pq.offer(new int[] { A[newi][newj], newi, newj });
                    A[newi][newj] = -1;
                }
            }
        }
        return maxscore;
    }
}