Submission #2230294

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Source Code Expand

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

int n, bel[100005];
set<int> edges[100005];
map<pair<int, int>, int> cnt;
queue<pair<int, int> > Queue;

template<typename T0, typename T1>
inline pair<T0, T1> get_id(T0 x, T1 y) {
	if (x > y) swap(x, y);
	return make_pair(x, y);
}

inline void go_fail() {
	puts("NO");
	exit(0);
}

void link_edges(int x, int y) {
	edges[x].insert(y);
	edges[y].insert(x);
	pair<int, int> id = get_id(x, y);
	++cnt[id];
	if (cnt[id] >= 3) go_fail();
	if (cnt[id] == 2) Queue.push(id);
}

inline int find(const int &x) {
	return bel[x] == x ? x : bel[x] = find(bel[x]);
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i < 2 * n - 1; ++i) {
		int x, y;
		scanf("%d%d", &x, &y);
		link_edges(x, y);
	}
	for (int i = 1; i <= n; ++i) bel[i] = i;
	for (int i = 1; i < n; ++i) {
		static int x, y;
		for (;;) {
			if (Queue.empty()) go_fail();
			x = Queue.front().first;
			y = Queue.front().second;
			Queue.pop();
			if (x != y) break;
		}
		if (edges[x].size() > edges[y].size()) swap(x, y);
		bel[x] = y;
		cnt.erase(get_id(x, y));
		edges[y].erase(x);
		for (auto v : edges[x]) {
			v = find(v);
			if (v == y) continue;
			cnt.erase(get_id(x, v));
			link_edges(v, y);
			edges[v].erase(x);
			edges[x].erase(v);
		}
	}
	puts("YES");
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:34:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
                 ^
./Main.cpp:37:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &x, &y);
                        ^

Judge Result