Dùng chặt nhị phân code c++ giúp mình bên dưới với: 

`\color{red}{\text{@hoangduy67}}`

#include <bits/stdc++.h>
using namespace std;
struct so{
    int giatri;
    int vitri;
};
so a[1000011];
int n,m,b[1000011];
bool cmp(so a, so b){
    return (a.giatri < b.giatri || (a.giatri == b.giatri && a.vitri < b.vitri));
}
int main()
{
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        cin>>a[i].giatri;
        a[i].vitri=i;
    }
    for(int i=1;i<=m;i++){
        cin>>b[i];
    }
    sort(a+1,a+n+1,cmp);
    for(int i=1;i<=m;i++){
        int x=b[i],d,c,g,res=0;
        d=1,c=n;
        while(d<=c){
            g=(d+c)/2;
            if(a[g].giatri==x){
                res=a[g].vitri;
                c=g-1;
            }else if(a[g].giatri>x) c=g-1;
            else d=g+1;
        }
        cout<<res<<" ";
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
  //freopen(".inp" , "r" , stdin);
  //freopen(".out" , "w", stdout);
  long long n, m;
  cin >> n >> m;
  vector<long long> a(n), b(m);
  vector<pair<long long, long long>> c(n);
  for (long long i = 0; i < n; ++i)
  {
    cin >> a[i];
    c[i] = {a[i], i + 1};
  }
  for (long long i = 0; i < m; ++i)
  {
    cin >> b[i];
  }
  sort (c . begin(), c . end());
  vector<long long> r(m);
  for (long long j = 0; j < m; ++j)
  {
    long long z = b[j];
    auto it = lower_bound(c . begin(), c . end(), make_pair(z, 0ll));
    if (it != c . end() and it -> first == z)
    {
      r[j] = it -> second;
    }
    else
    {
      r[j] = 0;
    }
  }
  for (long long i = 0; i < m; ++i)
  {
    if (i > 0) cout << " ";
    cout << r[i];
  }
}