题解 | 找x /find(beginit,endit,x);

#include <iostream>
#include<algorithm>
#include<vector>
#include<map>
#include<string>
using namespace std;//find(beginit,endit,x);
int main(){
	int n;
	while (cin >> n) {
		vector<int >v1;
		vector<int>::iterator it;
		
		int a;
		for (int i = 0; i < n; i++) {
			cin >> a;
			
			v1.push_back(a);
		}
		int x;
		cin >> x;
		it=find(v1.begin(), v1.end(), x);
		if (it == v1.end()) {
			cout << "-1"; return 0;
		}
		else {
			cout << it - v1.begin();
		}
	}
}