20分求助！玄关

传送门

#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m,a[100010],b[100010],cnt;
signed 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(a+1,a+n+1);
    sort(b+1,b+m+1);
    for(int i=1;i<=n;i++){
        int l=1,r=m,mid=(r+l)/2;
        while(l<=r){
            if(b[mid]==a[i]){
                cout<<a[i]<<" ";
                break;
            }
            else if(b[mid]<a[i]){
                l=mid+1;
                mid=(r+l)/2;
            } 
            else{
                r=mid-1;
                mid=(r+l)/2;
            }
        }
    }
    return 0;
}