POJ 2378 Tree Cutting 入門樹形dp dfs?

題意: 給出一棵樹, 現在去掉一個點, 問剩下的分離的每個連通塊的大小是不是小于總大小的一半, 把這樣的節點輸出.

思路:

人家說是樹dp, 但感覺是dfs啊...Orz

#include<cstdio>
#include<cstring>
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
vector<int>v[10005];
int n;
bool vis[10005]= {0};
int ans[10005]= {0};
int ansi=0;

int dfs(int x)
{
    vis[x]=1;
    int sum=0;
    int num=0;
    int flag=0;
    for(int i=0; i<v[x].size(); i++)
    {
        if(vis[v[x][i]]==0)
        {
            num=dfs(v[x][i]);
            sum+=num;
            if(num>n/2)
                flag=1;
        }
    }
    if(n-sum-1>n/2)
        flag=1;
    if(flag==0)
        ans[ansi++]=x;
    return sum+1;
}



int main()
{
    scanf("%d",&n);
    for(int i=0; i<n-1; i++)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs(1);
    if(ansi==0)
    {
        printf("NONE\n");
    }
    else
    {
        sort(ans,ans+ansi);
        for(int i=0; i<ansi; i++)
        {
            printf("%d\n",ans[i]);
        }
    }
}
           

照例貼新代碼, 感覺寫的更毒瘤了...

//#include<bits/stdc++.h>
#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;

void debug_out() {
    cerr << '\n';
}

template<typename T, typename ...R>
void debug_out(const T &f, const R &...r) {
    cerr << f << " ";
    debug_out(r...);
}

#define debug(...) cerr << "[" << #__VA_ARGS__ << "]: ", debug_out(__VA_ARGS__);

typedef long long ll;

const int M = 10005;
const int inf = 1e9 + 5;
const int mod = 1e9 + 7;

int n;
struct node {
    int v, nxt;
} edge[M*2];
int head[M];
int ei;
int ssum[M];

void addedge(int u, int v) {
    edge[ei].v = v;
    edge[ei].nxt = head[u];
    head[u] = ei++;
}

int fa[M];

int dfs(int x, int f) {
    int sum = 0;
    for (int i = head[x]; i != -1; i = edge[i].nxt) {
        int v = edge[i].v;
        if (fa[v] != x && fa[v] != 0)continue;
        fa[v] = x;
        sum += dfs(v, f);
    }
    return ssum[x] = sum + 1;
}

int hlf;

void init() {
    memset(head, -1, sizeof(head));
    ei = 0;
    scanf("%d", &n);
    hlf = n / 2;
    for (int i = 0; i < n - 1; i++) {
        int u, v;
        scanf("%d%d", &u, &v);
        addedge(u, v);
        addedge(v, u);
    }
}

void solve() {
    fa[1] = 1;
    dfs(1, 1);
    int hv = 0;
//
//    for (int i = 1; i <= n; i++) {
//        debug(i, ssum[i]);
//    }


    for (int i = 1; i <= n; i++) {
        int flag = 0;
        for (int j = head[i]; j != -1; j = edge[j].nxt) {
            int v = edge[j].v;
            if (fa[v] != i)continue;
            if (ssum[v] <= hlf);
            else {
//                debug(i,v,ssum[v]);
                flag = -1;
                break;
            }
        }
//        debug(i,n-ssum[i],flag);
        if (n - ssum[i] <= hlf && flag == 0) {
            hv = 1;
            printf("%d\n", i);
        }
    }
    if (hv == 0) {
        printf("NONE\n");
    }
}

int main() {

    init();

    solve();

    return 0;
}