题解

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

int main() {
	int n;
	cin >> n;
	vector<pair<char, int>> steps(n);
	for (auto &[dir, num_steps] : steps) { cin >> dir >> num_steps; }
	pair<int, int> curr{0, 0};
	map<pair<int, int>, int> visits{{curr, 0}};

	int time = 0;
	int max_regrow = INT32_MAX;
	for (const auto &[dir, num_steps] : steps) {
		pair<int, int> delta;
		switch (dir) {
		case 'N':
			delta = pair<int, int>{0, 1};
			break;
		case 'W':
			delta = pair<int, int>{-1, 0};
			break;
		case 'E':
			delta = pair<int, int>{1, 0};
			break;
		case 'S':
			delta = pair<int, int>{0, -1};
			break;
		}

		for (int i = 0; i < num_steps; i++) {
			curr = pair<int, int>{curr.first + delta.first,
			                      curr.second + delta.second};
			time++;
			if (visits.count(curr)) {
				max_regrow = min(max_regrow, time - visits[curr]);
			}
			visits[curr] = time;
		}
	}
	cout << (max_regrow == INT32_MAX ? -1 : max_regrow) << endl;
}