Submission #337991

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Source Code Expand

#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

#define pb push_back
#define mp make_pair
#define mod 1000000007
#define fi first
#define sc second
typedef long long ll;
typedef pair<int,int> P;

int n,m;
vector<P>ed;
int t[500005];

int par[400005];
int ran[400005];
void init()
{
	for(int i=0;i<400005;i++) par[i]=i,ran[i]=0;
}
int find(int x)
{
	if(par[x] == x) return x;
	else return par[x]=find(par[x]);
}
void unite(int x,int y)
{
	x=find(x);
	y=find(y);
	if(x == y) return ;
	if(ran[x]<ran[y]) par[x]=par[y];
	else 
	{
		par[y]=par[x];
		if(ran[x] == ran[y]) ran[x]++;
	}
}
bool same(int x,int y)
{
	return find(x)==find(y);
}

vector<P>edge[400005];
int p[400005];
bool d[500005];
int dfs(int v,int u)
{
	int ret = p[v];
	for(int i=0;i<edge[v].size();i++)
	{
		int x = edge[v][i].fi;
		if(x == u) continue;
		int a = dfs(x,v);
		ret += a;
		if(a%2 == 1) d[edge[v][i].sc] = true;
	}
	return ret;
}
int main()
{
	scanf("%d%d",&n,&m);
	t[0] = 1;
	for(int i=1;i<=500001;i++) t[i] = (t[i-1]*2)%mod;
	
	for(int i=0;i<m;i++)
	{
		int a,b; scanf("%d%d",&a,&b);
		ed.pb(mp(a,b));
		p[a] ^= 1;
		p[b] ^= 1;
	}
	init();
	for(int i=0;i<m;i++)
	{
		if(!same(ed[i].fi,ed[i].sc))
		{
			unite(ed[i].fi,ed[i].sc);
			edge[ed[i].fi].pb(mp(ed[i].sc,i));
			edge[ed[i].sc].pb(mp(ed[i].fi,i));
		}
	}
	dfs(1,-1);
	int res = 0;
	for(int i=0;i<m;i++)
	{
		if(d[i]) res = (res+t[i+2])%mod;
		else res = (res+t[i+1])%mod;
	}
	cout << res << endl;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:66:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
./Main.cpp:72:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]

Judge Result