778. Swim in Rising Water

class Solution {
    int[][] dirs = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
    public int swimInWater(int[][] grid) {
        int n = grid.length;
        int[][] dist = new int[n][n];
        for (int[] row : dist) {
            Arrays.fill(row, n * n);
        }
        dist[0][0] = grid[0][0];
        
        boolean[][] visited = new boolean[n][n];
        visited[0][0] = true;
        
        PriorityQueue<int[]> heap = new PriorityQueue<>((a, b) -> grid[a[0]][a[1]] - grid[b[0]][b[1]]);
        heap.offer(new int[]{0, 0});
        
        while (!heap.isEmpty()) {
            int[] cur = heap.poll();
            int row = cur[0], col = cur[1];
            if (row == n - 1 && col == n - 1) {
                return dist[row][col];
            }
            
            for (int[] dir : dirs) {
                int r = cur[0] + dir[0], c = cur[1] + dir[1];
                if (r >= 0 && r < n && c >= 0 && c < n && 
                    !visited[r][c] && dist[r][c] > Math.max(dist[row][col], grid[r][c])) {
                    visited[r][c] = true;
                    dist[r][c] = Math.max(dist[row][col], grid[r][c]);
                    heap.offer(new int[]{r, c});
                }
            }
        }
        
        return dist[n - 1][n - 1];
    }
}