Submission #1535384

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
//#define int long long

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned __int128 HASH;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll,int> plli;
typedef pair<double, int> pdbi;
typedef pair<int,pii> pipii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n);i>0;i--)
#define rrep2(i,a,b) for (int i=(a);i>b;i--)
#define pb push_back
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()

const ll mod = 1000000000 + 7;
const ll hmod1 = 999999937;
const ll hmod2 = 1000000000 + 9;
const ll INF = 1<<30;
const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};
const int dx8[8] = {1, 1, 1, 0, 0, -1, -1, -1};
const int dy8[8] = {0, 1, -1, 1, -1, 0, 1, -1};
const double pi = 3.141592653589793;

int n;
vector<vector<int>> g(100000 + 5);

pair<ll, ll> dfs(int now, int par) {
    pair<ll, ll> ret;
    ll wcnt = 1;
    ll bcnt = 1;
    for (auto to : g[now]) {
        if (to == par) continue;
        pair<ll, ll> tmp = dfs(to, now);
        (wcnt *= (tmp.fi + tmp.se)) %= mod;
        (bcnt *= tmp.fi)%= mod;
    }
    ret = make_pair(wcnt, bcnt);
    return ret;
}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    rep(i, n - 1) {
        int a, b;
        cin >> a >> b;
        a--; b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    pair<ll, ll> ans = dfs(0, -1);
    cout << (ans.fi + ans.se) % mod << endl;
}

Submission Info

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