题目
In a row of dominoes, A[i] and B[i] represent the top and bottom halves of the ith domino. (A domino is a tile with two numbers from 1 to 6 - one on each half of the tile.)
We may rotate the ith domino, so that A[i] and B[i] swap values.
Return the minimum number of rotations so that all the values in A are the same, or all the values in B are the same.
If it cannot be done, return -1.
解题思路
如果答案存在，那么答案一定是第一个骨牌上面的数或者下面的数，分别计算把所有骨牌都转成和这两个数在上面相同或者在下面相同，所需的旋转次数，返回最小值
代码
class Solution:
def minDominoRotations(self, A: List[int], B: List[int]) -> int:
def check(n):
reta = retb = 0
for i in range(len(A)):
if A[i] != n and B[i] != n:
return -1
if A[i] != n:
reta += 1
elif B[i] != n:
retb += 1
return min(reta, retb)
res = check(A[0])
if res != -1 or A[0] == B[0]:
return res
return check(B[0])
