#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 100010;
int a[N];
int b[N];
int SR(int x,int l,int r) {
    if(l >= r)
        return -1;
    while(l < r) {
        int mid = l + r + 1  >> 1;
        if(a[mid] <= x) {
            l = mid;
        }
        else r = mid - 1;
    }
    if(a[r]==x)return r;
    return -1;
}
int main () {
    int n ;
    cin >> n;
    for (int i = 1; i <= n; i ++) {
        cin >> a[i];
    }
    int m;
    cin >> m;
    for (int i = 1; i <= m ; i ++) {
        cin >> b[i];
    }
    for(int i = 1; i <= m; i ++) {
        cout << SR(b[i],0,n) <<' ';
    }
    return 0;
}

废话少说看代码

#include<bits/stdc++.h>

using namespace std;
const int N = 1e5 + 5;
int num1[N];

int main(void)
{
	int n, m;
	cin >> n;
	for (int i = 1; i <= n; i++) cin >> num1[i];
	cin >> m;
	for (int i = 0; i < m; i++)
	{
		int t,l;
		cin >> t;
		
		l = upper_bound(num1 + 1, num1 + 1 + n, t) - num1-1;
		if (num1[l] != t) cout << -1 << " ";
		else cout << l << " ";
	}


	return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=1e6+5;
int f[N];
int n,l,r,m,g;
int find(int k){
	l=1,r=n;
	while(l<=r){
		int mid=(l+r)/2;
		if(f[mid]<=k){
			l=mid+1;
		}
		else{
			r=mid-1;
		}
	}
	if(f[l-1]==k){
		return l-1;
	}
	else{
		return -1;
	}
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>f[i];
	}
	cin>>m;
	while(m--){
		int g;
		cin>>g;
		cout<<find(g)<<" ";
	}
	return 0;
}