算法训练 队列

#include<iostream>
#include<string>
using namespace std;
const int n = 100005;
int head, tail;
string queue[n];
void enqueue(string name) {
	queue[tail++] = name;//tail队尾的后一位
}
string dequeue() {
	return queue[head++];//返回头元素后 head++
}
string query(int pos) {
	return queue[head + pos - 1];
}

 
int main() {
	int n;
	cin >> n;
	while (n--) {
		int op;
		cin >> op;
		if (op == 1) {
			string name;
			cin >> name;
			enqueue(name);
		}
		else if (op == 2) {
			cout << dequeue() << endl;
		}
		else if (op == 3) {
			int pos;
			cin >> pos;
			cout << query(pos) << endl;
		}
	}

	return 0;
}