Educational Codeforces Round 56 (Rated for Div. 2) D

给你一个无向图 以及点的个数和边  每个节点只能用1 2 3 三个数字 求相邻

两个节点和为奇数   能否构成以及有多少种构成方法

#include<bits/stdc++.h>
using namespace std;
#define LL long long
#define maxn 300005
;
vector<int>q[maxn];
LL fa[maxn],sumx,sumy;
;
LL poww(LL a,LL b){
    LL ans = ;
    while(b){
        ){
            ans = ans*a%mod;
        }
        b/=;
        a = a*a%mod;
    }
    return ans%mod;
}
void dfs(int u,int deep){
    ) return ;
    ;j<q[u].size();j++){
        int v = q[u][j];
        ){
            fa[v] = -deep;
            sumx++;
            ) sumy++;
            dfs(v,-deep);
        }else{
            -deep)!=fa[v]){
                flag = ;
                return ;
            }
        }
    }
}
int main(){
    int t;
    cin>>t;
    while(t--){
        flag = ;
        int n,m;
        scanf("%d%d",&n,&m);
        LL ans = ;
        vector<int>s,z;
        ;j<=n;j++){
            q[j].clear();
            fa[j]=-;
        }
        ;j<m;j++){
            int u,v;
            scanf("%d%d",&u,&v);
            q[u].push_back(v);
            q[v].push_back(u);
        }
        ;j<=n;j++){
            sumx = ,sumy = ;
            ){
                fa[j]=;
                dfs(j,);
                ans = (ans*(poww(1LL*,1LL*sumy)+poww(1LL*,1LL*(sumx-sumy)))%mod)%mod;
            }
        }
        if(flag){
            ans = ;
        }
        cout<<ans<<endl;

    }
}