Back From Summer '19 P2: Straying From God's Light

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Points: 7 (partial)
Time limit: 1.0s
Java 1.8s
Memory limit: 128M

Problem type

Marcus is stuck in a 2-dimensional grid of size N \times N, consisting of . for walkable spaces and # for unwalkable spaces! He is at the top left corner (position (1, 1)) and must travel to the bottom right corner (position (N, N)) through only walkable spaces. He can only move left, right, and down. In a path, let D, L, R be the number of times he moves down, left, and right, respectively. Let the cost of the path be D^2 + L^2 + R^2. Marcus wants to find a path from (1, 1) to (N, N) that has the minimum cost.

Marcus wants to know the minimum possible cost. Please help him!

Input Specification

The first line will contain the integer N (1 \le N \le 1000), the size of the grid.

The next N lines will each contain N characters, either . for a walkable space or # for an unwalkable space. The first character of the first line will be position (1, 1) and the N^\text{th} character of the N^\text{th} line will be position (N, N).

It is guaranteed positions (1, 1) and (N, N) will be walkable (.).

Output Specification

Output the minimum cost path for Marcus. If there is no path, output -1.


Subtask 1 [25%]

N \le 25

Subtask 2 [75%]

No additional constraints.

Sample Input


Sample Output


Explanation For Sample

The minimum cost path consists of moving down D = 5 units, left L = 2 units, and right R = 7 units, for a total of 5^2 + 2^2 + 7^2 = 78.


  • 0
    KhalilTlili  commented on March 27, 2021, 9:44 a.m.

    Pls someone help i'm getting WA in test case 12 i dont know why. THANKS!

  • 61
    piddddgy  commented on Sept. 3, 2019, 6:54 p.m. edit 2