Submission #338431

---

Source Code Expand

#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v, w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;
int INF = INT_MAX / 2;

struct union_find {
	vector<int> v;
	union_find(int n) : v(n, -1) {}
	int find(int x) { return (v[x] < 0) ? x : (v[x] = find(v[x])); }
	void unite(int x, int y) {
		x = find(x); y = find(y);
		if (x != y) {
			if (-v[x] < -v[y]) swap(x, y);
			v[x] += v[y]; v[y] = x;
		}
	}
	bool same(int x, int y) { return find(x) == find(y); }
	int size(int x) { return -v[find(x)]; }
};

void f(int u, int p, vector< vector<int> >& G, vector<int>& d, vector<int>& dep, vector<int>& x) {
	if (p != -1) dep[u] = dep[p] + 1;
	if (d[u] % 2 == 1) x[u]++;
	for (int i = 0; i < G[u].size(); i++) {
		int v = G[u][i];
		if (v == p) continue;
		f(v, u, G, d, dep, x);
		x[u] += x[v];
	}
}

int main() {
	int N, M; cin >> N >> M;
	vector<ll> w(M);
	w[0] = 2;
	for (int i = 1; i < M; i++)
		w[i] = w[i - 1] * 2 % MOD;
	vector<int> A(M), B(M);
	vector<int> d(N);
	union_find uf(N);
	vector<int> a;
	vector< vector<int> > G(N);
	ll ans = 0;
	for (int i = 0; i < M; i++) {
		int& u = A[i], &v = B[i];
		scanf("%d%d", &u, &v);
		u--; v--;
		d[u]++; d[v]++;
		if (!uf.same(u, v)) {
			uf.unite(u, v);
			a.push_back(i);
			G[u].push_back(v);
			G[v].push_back(u);
		}
		ans += w[i];
	}
	vector<int> dep(N), x(N);
	f(0, -1, G, d, dep, x);
	for (int j = 0; j < a.size(); j++) {
		int i = a[j], u = A[i], v = B[i];
		if (dep[u] < dep[v]) swap(u, v);
		if (x[u] % 2 == 1) ans += w[i];
	}
	cout << ans % MOD << endl;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:74:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]

Judge Result