pku2378 Tree Cutting

http://poj.org/problem?id=2378

树状DP

#include <stdio.h>
#include <string.h>
#include <vector>
#include <set>

#define N 10010

using namespace std;

vector<int> a[N];
set<int> set1;
set<int>::iterator it;

int n, father[N] = {0};

int dfs(int x)
{
    int i, j, flag = 0, sum = 1, temp;
    //printf("%d: ( ", x);
    for(i=0; i<a[x].size(); i++)
    {
        j = a[x][i];
        if(!father[j])
        {
            father[j] = x;
            temp = dfs(j);
            sum += temp;
            if(temp > n/2)
            {
                flag = 1;
            }
        }
    }
    if(n - sum > n/2)
    {
        flag = 1;
    }
    if(flag == 0)
    {
        set1.insert(x);
    }
    //printf(" %d) ", dp[x]);
    return sum;
}

int main()
{
    int i, x, y;
    scanf("%d", &n);
    for(i=1; i<=n-1; i++)
    {
        scanf("%d%d", &x, &y);
        a[x].push_back(y);
        a[y].push_back(x);
    }
    father[1] = 1;
    dfs(1);
    for(it=set1.begin(); it!=set1.end(); it++)
    {
        printf("%d\n", *it);
    }
    return 0;
}