Submission #1520795

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Source Code Expand

#include<iostream>
#include<iomanip>
#include<math.h>
#include<vector>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<complex>
#include<unordered_map>

#define INF 1000000000ll
#define MOD 1000000007ll
#define EPS 1e-8

#define REP(i, m) for(long long i = 0; i < m; ++i)
#define FOR(i, n, m) for(long long i = n; i < m; ++i)
#define ALL(v) v.begin(), v.end()
#define pb push_back

using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef long double ld;

vector<vector<int> > adj;
vector<vector<ll> > memo;
ll dfs(int pos, int c, int b) {
	if(memo[pos][c]!=INF*INF) return memo[pos][c];
	ll res=1;
	REP(i,adj[pos].size()) {
		if(adj[pos][i]!=b) {
			if(c==0) res*=dfs(adj[pos][i],0,pos)+dfs(adj[pos][i],1,pos);
			else res*=dfs(adj[pos][i],0,pos);
		}
	}
	return memo[pos][c]=res%MOD;
}

int main() {
	int n;
	cin>>n;
	adj.resize(n);
	memo.resize(n);
	REP(i,n) {
		memo[i].resize(2);
		REP(j,2) memo[i][j]=INF*INF;
	}
	REP(i,n-1) {
		int a,b;
		cin>>a>>b;
		--a;
		--b;
		adj[a].pb(b);
		adj[b].pb(a);
	}
	cout<<dfs(0,0,-1)+dfs(0,1,-1)<<endl;
}

Submission Info

Judge Result