lc 765. Couples Holding Hands

first of all, we can prove that a exchange without any couple emerging is useless.
then we can prove in a couple position like row[6]=11,row[7]=23 , it's identical to fecth 10 or 22.
so this problem turns to be the one that needs you arrange an array of 0~n to it's right index.
you only need to record the exchange num.


class Solution:
    def mate(self,i):
        return i^1
    def minSwapsCouples(self, row):
        l=len(row)
        loc=[0]*l
        done=[False]*l
        for i in range(l):
            loc[row[i]]=i
        ans=0
        for i in range(l//2):
            j=i*2
            while not (row[j]^row[j^1]==1 or done[j]):
                ans+=1
                m=row[j]^1
                l=loc[m]
                row[l]=row[j^1]
                row[j^1]=m
                j=l
        # print(ans)
        return ans