Problem: There is a grid with N rows and N columns of squares. Let (i,j) be the square at the i-th row from the top and the j-th column from the left.  These squares have to be painted in one of the C colors from Color 1 to Color C. Initially, (i,j) is painted in Color c_{i,j}.  We say the grid is a _good_ grid when the following condition is met for all i,j,x,y satisfying 1 \leq i,j,x,y \leq N:    * If (i+j) \% 3=(x+y) \% 3, the color of (i,j) and the color of (x,y) are the same.   * If (i+j) \% 3 \neq (x+y) \% 3, the color of (i,j) and the color of (x,y) are different.  Here, X \% Y represents X modulo Y.  We will repaint zero or more squares so that the grid will be a good grid.  For a square, the _wrongness_ when the color of the square is X before repainting and Y after repainting, is D_{X,Y}.  Find the minimum possible sum of the wrongness of all the squares.

Submission attempts (in order):
import numpy as np
N, C = map(int, input().split())
D = np.array(list(map(int, input().split())), dtype=int)
for i in range(C-1):
    D = np.vstack((D, np.array(list(map(int, input().split())), dtype=int)))
Z = np.array(list(map(int, input().split())), dtype=int)
for i in range(N-1):
    Z = np.vstack((Z, np.array(list(map(int, input().split())), dtype=int)))
num = np.zeros((3,C), dtype=int)
for i in range(3):
    X = np.array([[(x+y+2)%3==i for y in range(N)] for x in range(N)])
    for c in range(C):
        Y = (Z*X)==c+1
        num[i,c] = Y.sum()
costs = np.dot(num, D.T)
mincost = 10**10
for c0 in range(C):
    for c1 in range(C):
        if c1 ==c0:
            continue
        for c2 in range(C):
            if c2 == c1:
                continue
            cost = costs[0,c0]+costs[1,c1]+costs[2,c2]
            mincost = min(mincost, cost)
print(mincost)

import numpy as np
N, C = map(int, input().split())
D = np.array(map(int, input().split()), dtype=int)
for i in range(C-1):
    D = np.vstack((D, np.array(map(int, input().split()), dtype=int)))
Z = np.array(map(int, input().split()), dtype=int)
for i in range(N-1):
    Z = np.vstack((c, np.array(map(int, input().split()), dtype=int)))
num = np.zeros(size=(3,C), dtype=int)
for i in range(3):
    X = np.array([[(x+y+2)%3==i for y in range(N)] for x in range(N)])
    for c in range(C):
        Y = (Z*X)==c+1
        num[i,c] = Y.sum()
costs = np.matmul(num, D)
mincost = 10**10
for c0 in range(C):
    for c1 in range(C):
        if c1 ==c0:
            continue
        for c2 in range(C):
            if c2 == c1:
                continue
            cost = costs[0,c0]+costs[1,c1]+costs[2,c2]
            mincost = min(mincost, cost)
print(mincost)

import numpy as np
N, C = map(int, input().split())
D = np.array(list(map(int, input().split())), dtype=int)
for i in range(C-1):
    D = np.vstack((D, np.array(list(map(int, input().split())), dtype=int)))
Z = np.array(list(map(int, input().split())), dtype=int)
for i in range(N-1):
    Z = np.vstack((Z, np.array(list(map(int, input().split())), dtype=int)))
num = np.zeros((3,C), dtype=int)
for i in range(3):
    X = np.array([[(x+y+2)%3==i for y in range(N)] for x in range(N)])
    for c in range(C):
        Y = ((Z*X)==(c+1))
        num[i,c] = Y.sum()
costs = np.dot(num, D)
mincost = 10**10
for c0 in range(C):
    for c1 in range(C):
        if c1 ==c0:
            continue
        for c2 in range(C):
            if c2 == c0 or c2 == c1:
                continue
            cost = costs[0,c0]+costs[1,c1]+costs[2,c2]
            mincost = min(mincost, cost)
print(mincost)

Verdicts: Wrong Answer

Runtime Error

Accepted