（每日一练28817）题目名称：交换后的or

[文盲老顾]

给定两组长度为n的二进制串，请问有多少种方法在第一个串中交换两个不同位置上的数字，使得这两个二进制串“或”的结果发生改变？

嗯。。。题解太多了，就是分成4种情况，然后各自统计有多少数量，同时累加即可

n = int(input())
s1,s2 = input(),input()
arr,ans = [0,0,0,0],0
for i in range(n):
    if s1[i] == s2[i] == '1':
        arr[0] += 1
        ans += arr[3]
    elif s1[i] == s2[i] == '0':
        arr[3] += 1
        ans += arr[0] + arr[1]
    elif s1[i] == '1':
        arr[1] += 1
        ans += arr[3] + arr[2]
    else:
        arr[2] += 1
        ans += arr[1]
print(ans)

[文盲老顾]

n = int(input())
s1,s2 = input(),input()
arr,ans = [0,0,0,0,'11','10','01','00',(3,),(2,3),(1,),(0,1)],0
for i in range(n):
    for j in range(4,8):
        if s1[i] == arr[j][0] and s2[i] == arr[j][1]:
            arr[j - 4] += 1
            ans += sum([arr[v] for v in arr[j + 4]])
print(ans)