玄学，为何简单版20pts复杂版30pts还有一个样例不过？

如题，求条。 代码如下：

#include <algorithm>
#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;

long long a[500005], b[500005];

int main() {
    int n, m, ans = 0, cnt = 0;
    cin >> n >> m;
    for (int i = 1; i <= n; i ++) {
        cin >> a[i];
    }
    for (int i = 1; i <= m; i ++) {
        cin >> b[i];
    }
    sort(a + 1, a + n + 1);
    sort(b + 1, b + n + 1);
    for (int i = 1; i <= n; i ++, cnt ++) {
        if (b[lower_bound(b + 1, b + n + 1, a[i]) - b] == a[i]) {
            if (cnt) {
                ans ++;
            }
            cnt = -1;
        }
    }
    if (cnt) {
        ans ++;
    }
    cout << ans;
    return 0;
}