Submission #1689265

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
const int mod=1e9+7;
int fastpow(int x,int a){
	int ret=1;
	while(a){
		if(a&1) ret=ret*1LL*x%mod;
		a>>=1;x=x*1LL*x%mod;
	}
	return ret;
}
#define LL long long
struct Combin{
	#define N 405
	int fac[N],rv[N],facrv[N];
	Combin(){
		fac[0]=rv[1]=facrv[0]=1;
		for(int i=2;i<N;i++) rv[i]=((-(LL)(mod/i)*rv[mod%i]%mod)+mod)%mod;
		for(int i=1;i<N;i++) fac[i]=(LL)fac[i-1]*i%mod;
		for(int i=1;i<N;i++) facrv[i]=(LL)facrv[i-1]*rv[i]%mod;
	}
	int C(int r1,int n1){
		if(r1>n1) return 0;
		return fac[n1]*(LL)facrv[r1]%mod*facrv[n1-r1]%mod;
	}
	#undef N
}C;
#define N 55 
struct edge{
	int t,next;
}e[205];int ecnt,head[N],du[N];
void addedge(int f,int t){
	e[++ecnt]=(edge){t,head[f]};head[f]=ecnt;du[f]++;
	e[++ecnt]=(edge){f,head[t]};head[t]=ecnt;du[t]++;
}
int n,m,k;
int ans=1;
void calc2(int sz){
	int ret=0;
	for(int i=1;i<=sz;i++)
		ret=(ret+fastpow(k,__gcd(sz,i)))%mod;
	ans=ans*1LL*(ret*1LL*C.rv[sz]%mod)%mod;
}
void calc3(int sz){
	ans=ans*1LL*C.C(k-1,sz+k-1)%mod;
}

int sz[N],mint[N],ti[N],tcnt,etcnt,vis[N];
int top,sta[205];
void tarjan(int u,int fre){
	ti[u]=++tcnt;mint[u]=ti[u];
	int mn=ti[u];
	for(int i=head[u];i;i=e[i].next){
		if((i^fre)==1) continue;
		if(ti[e[i].t]==0){
			sta[++top]=i;
			tarjan(e[i].t,i);
			mn=min(mn,mint[e[i].t]);
			if(mint[e[i].t]>=ti[u]){
				int n1=0,m1=0;
				etcnt++;
				while(top>0&&sta[top]!=fre&&mint[e[sta[top]].t]>=ti[u]){
					m1++;
					if(vis[e[sta[top]].t]!=etcnt) n1++,vis[e[sta[top]].t]=etcnt;
					if(vis[e[sta[top]^1].t]!=etcnt) n1++,vis[e[sta[top]^1].t]=etcnt;
					top--;
				}
				if(m1==1) ans=ans*1LL*k%mod;
				else if(n1==m1) calc2(m1);
				else calc3(m1);
			}
		}else{
			if(ti[u]>ti[e[i].t]) sta[++top]=i;
			mn=min(mn,mint[e[i].t]);
		}
	}
	mint[u]=mn;
}

int main(){
	ecnt=1;
	scanf("%d%d%d",&n,&m,&k);
	for(int i=1,f,t;i<=m;i++) scanf("%d%d",&f,&t),addedge(f,t);
	for(int i=1;i<=n;i++)
		if(ti[i]==0)
			tarjan(i,0);	

	cout<<(ans+mod)%mod<<endl;
	return 0;
} 

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:82:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d",&n,&m,&k);
                          ^
./Main.cpp:83:60: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1,f,t;i<=m;i++) scanf("%d%d",&f,&t),addedge(f,t);
                                                            ^

Judge Result