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):
from itertools import product
from collections import Counter
 
n, c = map(int, input().split())
color_costs = [list(map(int, input().split())) for _ in range(c)]
matrix = [list(map(int, input().split())) for _ in range(n)]
 
colord = {(i, j):cost for i, row in enumerate(color_costs)
                      for j, cost in enumerate(row)}
 
res = []
for n in range(3):
  color_count = Counter(c-1 for i, row in enumerate(matrix) 
                            for j, c in enumerate(row) 
                            if (i + j) % 3 == n)
  def color_cost(color):
    return sum(colord[ccolor, color] * ccount for ccolor, ccount in color_count.items())
  cx = [(color, color_cost(color)) for color in range(c)]
  sorted_by_cost = sorted(cx, key=lambda x:x[1])
  cheapest3 = sorted_by_cost[:3]
  res.append(cheapest3)
 
color_pickss = product(*res)
filtered_unique = (picks for picks in color_pickss if len(set(x[0] for x in picks)) == 3)
costs = (sum(x[1] for x in picks) for pick in filtered_unique)
print(min(costs))
from itertools import product
from collections import Counter
 
n, c = map(int, input().split())
color_costs = [list(map(int, input().split())) for _ in range(c)]
matrix = [list(map(int, input().split())) for _ in range(n)]

colord = {(i, j):cost for i, row in enumerate(color_costs)
                      for j, cost in enumerate(row)}
 
res = []
for n in range(3):
  color_count = Counter(c-1 for i, row in enumerate(matrix) 
                            for j, c in enumerate(row) 
                            if (i + j) % 3 == n)
  def color_cost(color):
    return sum(colord[ccolor, color] * ccount for ccolor, ccount in color_count.items())
  cx = [(color, color_cost(color)) for color in range(c)]
  sorted_by_cost = sorted(cx, key=lambda x:x[1])
  cheapest3 = sorted_by_cost[:3]
  res.append(cheapest3)

color_pickss = product(*res)
filtered_unique = (picks for picks in color_pickss if len(set(x[0] for x in picks)) == 3)
costs = (sum(x[1] for x in picks) for picks in filtered_unique)
print(min(costs))

from itertools import product
from collections import Counter
 
n, c = map(int, input().split())
color_costs = [list(map(int, input().split())) for _ in range(c)]
matrix = [list(map(int, input().split())) for _ in range(n)]

colord = {(i, j):cost for i, row in enumerate(color_costs)
                      for j, cost in enumerate(row)}
 
res = []
for n in range(3):
  color_count = Counter(c-1 for i, row in enumerate(matrix) 
                            for j, c in enumerate(row) 
                            if (i + j) % 3 == n)
  def color_cost(color):
    return sum(colord[ccolor, color] * ccount for ccolor, ccount in color_count.items())
  cx = [(color, color_cost(color)) for color in range(c)]
  sorted_by_cost = sorted(cx, key=lambda x:x[1])
  cheapest3 = sorted_by_cost[:3]
  res.append(cheapest3)

color_pickss = product(*res)
filtered_unique = (picks for picks in color_pickss if len(set(x[0] for x in picks)) == 3)
costs = (sum(x[1] for x in picks) for pick in filtered_unique)
print(min(costs))

from itertools import product
from collections import Counter
 
n, c = map(int, input().split())
color_costs = [list(map(int, input().split())) for _ in range(c)]
matrix = [list(map(int, input().split())) for _ in range(n)]

colord = {(i, j):cost for i, row in enumerate(color_costs)
                      for j, cost in enumerate(row)}
 
res = []
for n in range(3):
  color_count = Counter(c-1 for i, row in enumerate(matrix) 
                            for j, c in enumerate(row) 
                            if (i + j) % 3 == n)
  def color_cost(color):
    return sum(colord[ccolor, color] * ccount for ccolor, ccount in color_count.items())
  cx = [(color, color_cost(color)) for color in range(c)]
  sorted_by_cost = sorted(cx, key=lambda x:x[1])
  cheapest3 = sorted_by_cost[:3]
  res.append(cheapest3)

color_pickss = product(*res)
filtered_unique = (picks for picks in color_pickss if len(set(x[0] for x in picks)) == 3)
costs = (sum(x[1] for x in picks) for picks in filtered_unique)
print(min(costs))

Verdicts: Runtime Error

Runtime Error

Accepted