Submission #2230391

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Source Code Expand

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

int n;
set<pair<int, bool> > edges[100001];

int main() {
	stack<pair<int, int> > stk;
	scanf("%d", &n);
	for (int i = 1; i < n; ++i) {
		int x, y;
		scanf("%d%d", &x, &y), --x, --y;
		edges[x].insert(make_pair(y, 0));
		edges[y].insert(make_pair(x, 0));
	}
	for (int i = 1; i < n; ++i) {
		int x, y;
		scanf("%d%d", &x, &y), --x, --y;
		edges[x].insert(make_pair(y, 1));
		edges[y].insert(make_pair(x, 1));
		stk.push(make_pair(x, y));
	}
	int cnt = 0;
	while (!stk.empty()) {
		pair<int, int> edge = stk.top();
		stk.pop();
		int x = edge.first, y = edge.second;
		auto it = edges[x].find(make_pair(y, 0));
		if (it != edges[x].end()) {
			__typeof(it) it2 = it;
			++it2;
			if (it2 != edges[x].end() && it2->first == y) {
				if (edges[x].size() < edges[y].size()) swap(x, y);
				++cnt;
				edges[x].erase(make_pair(y, 0));
				edges[x].erase(make_pair(y, 1));
				edges[y].erase(make_pair(x, 0));
				edges[y].erase(make_pair(x, 1));
				for (auto it3 = edges[y].begin(); it3 != edges[y].end();) {
					stk.push(make_pair(x, it3->first));
					edges[it3->first].erase(make_pair(y, it3->second));
					edges[it3->first].insert(make_pair(x, it3->second));
					edges[x].insert(*it3);
					it3 = edges[y].erase(it3);
				}
			}
		}
	}
	puts(cnt == n - 1 ? "YES" : "NO");
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:9:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
                 ^
./Main.cpp:12:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &x, &y), --x, --y;
                                  ^
./Main.cpp:18:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &x, &y), --x, --y;
                                  ^

Judge Result