B.Last Year‘s Substring

https://codeforces.ml/contest/1462/problem/B

题意就是判断一串字符串中，经过n次删除一段连续的字符串的操作之后，使字符串变为”2020“，如果n<=1,输出”YES“，否则输出"NO"。观察一下就能发现可行的情况无非就是以下五种：

1. XXX2020
2. 2XXX020
3. 20XXX20
4. 202XXX0
5. 2020XXX

想得到的话，就能A了…

#include <bits/stdc++.h>
using namespace std;

int main() {
	int t;
	cin >> t;
	while (t--) {
		int n;
		string s;
		cin >> n;
		cin >> s;
		if (s[0] == '2' && s[1] == '0' && s[2] == '2' && s[3] == '0')
			cout << "YES" << endl;
		else if (s[0] == '2' && s[n - 3] == '0' && s[n - 2] == '2' && s[n - 1] == '0')
			cout << "YES" << endl;
		else if (s[0] == '2' && s[1] == '0' && s[n - 2] == '2' && s[n - 1] == '0')
			cout << "YES" << endl;
		else if (s[0] == '2' && s[1] == '0' && s[2] == '2' && s[n - 1] == '0')
			cout << "YES" << endl;
		else if (s[n - 4] == '2' && s[n - 3] == '0' && s[n - 2] == '2' && s[n - 1] == '0')
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	return 0;
}