Swim in Rising Water — hard DSA Problem

You are given an n x n integer matrix grid where each value grid[i][j] represents the elevation at that point (0,0). The rain starts at time = 0. At time t, the depth of the water everywhere is t. You can swim from a square to another 4-directionally adjacent square if and only if the elevation of both squares individually are at most t. Find the least time t at which you can swim from the top left (0, 0) to the bottom right (n-1, n-1).

Example 1:

Input:
2
0 2
1 3
Output: 3

Example 2:

Input:
5
0 1 2 3 4
24 23 22 21 5
12 13 14 15 16
11 17 18 19 20
10 9 8 7 6
Output: 16

Constraints:

n == grid.length == grid[i].length
1 ≤ n ≤ 50
0 ≤ grid[i][j] < n²
All values are unique

Input format: First line: n. Then n lines with n space-separated integers.

Output format: Minimum time.