codeforces round#527(div3) C. Prefixes and Suffixes STL做法

看到这种STL暴力法，构造出三个set，一个列举前缀，一个后缀，一个前缀后缀都塞进去，然后直接判断set==set，省去了好多麻烦

#include <bits/stdc++.h>

using namespace std;

int n;
vector<string> v;

string res;

bool check(const string &pref, const string &suf) {
	string s = pref + suf.substr(n - 2);
	set<string> vv, sPref, sSuf;
	for (int i = 0; i < n - 1; ++i) {
		sPref.insert(s.substr(0, n - i - 1));
		vv.insert(s.substr(0, n - i - 1));
		sSuf.insert(s.substr(i + 1));
		vv.insert(s.substr(i + 1));
	}
	if (vv == set<string>(v.begin(), v.end())) {
		for (int i = 0; i < 2 * n - 2; ++i) {
			if (sPref.count(v[i])) {
				res += 'P';
				sPref.erase(sPref.find(v[i]));
			} else if (sSuf.count(v[i])) {
				res += 'S';
				sSuf.erase(sSuf.find(v[i]));
			} 
		}
		return true;
	}
	return false;
}

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	cin >> n;
	v = vector<string>(2 * n - 2);
	vector<string> big;
	for (int i = 0; i < 2 * n - 2; ++i) {
		cin >> v[i];
		if (int(v[i].size()) == n - 1) {
			big.push_back(v[i]);
		}
	}
	
	if (check(big[0], big[1])) {
		cout << res << endl;
	} else {
		check(big[1], big[0]);
		cout << res << endl;
	}
	
	return 0;
}