SPOJ PT07X

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

const int OO = 1e9;
const double EPS = 1e-9;

int n;
vector<vector<int>> graph;

int mem[1000000][2];

int solve(int idx, int rem, int p) {
    if(mem[idx][rem] != -1) {
        return mem[idx][rem];
    }
    int &ret = mem[idx][rem];
    ret = rem;
    for(int e : graph[idx]) {
        if(e != p)
            if(rem)
                ret += min(solve(e,0,idx),solve(e,1,idx));
            else
                ret += solve(e,1,idx);
    }
    return ret;
}

int main()
{
    ios_base::sync_with_stdio(NULL);
    cin.tie(0);
    cout.tie(0);
    cin >> n;
    memset(mem,-1,sizeof(mem));
    graph.resize(n);
    for(int i = 0; i < n-1; i++) {
        int a,b;
        cin >> a >> b;
        a--,b--;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    cout << min(solve(0,0,-1),solve(0,1,-1)) << "\n";
    return 0;
}