求助！！！ WA#6

90分代码如下：

#include <bits/stdc++.h>
using namespace std;
long long n,m,x,a[500005],b[500005],ans;
bool check(long long k) 
{
    b[0]=-1e9,b[m+1]=1e9;
    long long l = 1,r = m,mid;
    while(l+1< r)
    {
        mid = (l + r) / 2;
        if (k < b[mid])
        {
            r = mid;
        }
        else if(k > b[mid])
        {
            l = mid;
        }
        else 
        {
            return 1;
        }
    }
    return 0;
}
int main()
{
    cin >> n >> m;
    for(int i = 1;i <= n;i++) 
    {
        cin >>a[i];
    }
    for(int i = 1;i <= m;i++) 
    {
        cin >> b[i];
    }
    sort(b +1,b + m + 1);
    if(!check(a[n])) 
    {   
        ans++;
    }
    for(int i = 1;i < n;i++)
    {
        if(!check(a[i]) && check(a[i + 1]))
        {
            ans++;
        }
    }
    cout << ans;
    return 0;
}