URAL1018 Binary Apple Tree

非常经典的树形DP(假设不会树形DP建议先看下面..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.......

建树我认为非常费劲,,,毕竟不太会........DP比較好理解吧,,,,,,,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;
}