听取RE声一片 源代码

#include<iostream>
#include<list>
#define traverse auto it = l.begin(); it != l.end(); it++
using namespace std;
int q;
list<int> l;
int main() {
	cin >> q;
	l.push_back(1);
	while (q--) {
		int op;
		cin >> op;
		if (op == 1) {
			int x, y;
			cin >> x >> y;
			for (traverse) {
				if (*it == x) {
					l.insert(++it, y);
					break;
				}
			}
		}
		else if (op == 2) {
			int x;
			cin >> x;
			for (traverse) {
				if (*it == x) {
					cout << *(++it) << endl;
					break;
				}
			}
		}
		else {
			int x;
			cin >> x;
			for (traverse) {
				if (*it == x) {
					l.erase(++it);
				}
			}
		}
	}
	return 0;
}