URAL1018 Binary Apple Tree

很经典的树形DP(如果不会树形DP建议先看以下..我就是先看了别的题,,握手的什么的)

给一棵树,留下N条边(它若留下边父亲的边比留下),,问最后苹果最多多少个.......

建树我觉得很费劲,,,毕竟不太会........DP比较好理解吧,,,,,,,就是多想一想把,,,,,当作模板题记录下来~~~~

#include <iostream>

#include <cstdio>

#include <bits/stdc++.h>

using namespace std;

const int maxn=101,maxq=100;

int n;//jieidanshu

int q;//baoliudebian

int g[maxn][maxn];//juzhenbiaoshiliangdianguanxi

int son[maxn][2]; //zijiedian

int apple[maxn]; //jiluzijieidanshang de pingguoshu

int dp[maxn][maxn]; //jiyihua

int flag[maxn];  //biaoji

int isleaf[maxn]; //jilushifouziye

void create(int root)

{

    int i,ct=0;

    for(i=1;i<=n;i++)

    {

        if(g[root][i]!=-1&&flag[i]==0) //zhaodaoleziye

        {

            son[root][ct++] = i; //diyigehuozhediergeziye

            apple[i]=g[root][i];

            flag[i] = 1;

            create(i); //jixujianshu

        }

    }

    if(ct==0)//meiyouziye

    {

        isleaf[root]=1;

    }

}

int treedp(int root, int num) //num biaoshi shengxiade dianshu

{

    if(num==0) return 0; //bushengxia

    if(isleaf[root]==1) return apple[root]; //zuihouyihang

    if(dp[root][num]!=-1) return dp[root][num];  //jiyihua

    int i,temp=0;

    for(i=0;i<num;i++)

    {

        temp=max(temp,treedp(son[root][0],i)+treedp(son[root][1],num-1-i));

    }

    dp[root][num]=temp+apple[root];

    //printf("%d**\n",dp[root][num]);

    return dp[root][num];

}

int main()

{

    int i,x,y,w;

    memset(g,-1,sizeof(g));

    scanf("%d%d",&n,&q);

    for(i=1;i<=n-1;i++)

    {

        scanf("%d%d%d",&x,&y,&w);

        g[x][y]=w;//zhelihenzhongyaodexiangfa!

        g[y][x]=w;

    }

    memset(flag,0,sizeof(flag));

    memset(isleaf,0,sizeof(isleaf));

    flag[1]=1;// 1 shi morende

    apple[1]=0;

    create(1);

    memset(dp,-1,sizeof(dp));

    printf("%d\n",treedp(1,q+1));

    return 0;

}