hdu 1011 Starship Troopers(树形dp)

http://acm.hdu.edu.cn/showproblem.php?pid=1011

dp[i][j]表示在第i个位置放j个trooper，然后又该节点分配给子节点后所能得到的最大brains;

状态转移方程dp[i][j]=max(dp[i][j],dp[i][j-k]+dp[son[i]][k]);

从叶子节点往根节点递推。。。

View Code

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
#include <cstring>
#define maxn 107
using namespace std;
struct node
{
    int bugs;
    int brain;
}tagp[maxn];
vector<int>g[maxn];//尝试stl的vector
int n,m,dp[maxn][maxn],visit[maxn];

void dfs(int pos)
{
    int i,j;
    visit[pos] = true;
    int nleast = (tagp[pos].bugs + 19)/20;//一个对付20个，计算最少需要多少个trooper
    for (i = nleast; i <= m; ++i)
    {
        dp[pos][i] = tagp[pos].brain;
    }
    for (i = 0; i < g[pos].size(); ++i)//递归的求解
    {
        int p = g[pos][i];
        if(visit[p])
        continue;
        dfs(p);
        for (j = m; j >= nleast; --j)
        {
            for (int k = 1; k + j <= m; ++k)
            if(dp[p][k])
            dp[pos][j+k] = max(dp[pos][j+k],dp[pos][j]+dp[p][k]);
        }
    }
}
int main()
{
    int i,a,b;
    while (scanf("%d%d",&n,&m))
    {
        if (n == -1&&m == -1)
        break;
        for (i = 1; i <= n; ++i)
        {
            scanf("%d%d",&tagp[i].bugs,&tagp[i].brain);
            g[i].clear();//更新
        }
        for (i = 0; i < n-1; ++i)
        {
            scanf("%d%d",&a,&b);
            g[a].push_back(b);//建图
            g[b].push_back(a);
        }
        if (m == 0)//注意这里优化处理
        {
            puts("0");
            continue;
        }
        memset(visit,false,sizeof(visit));
        memset(dp,0,sizeof(dp));
        dfs(1);
        printf("%d\n",dp[1][m]);
    }
    return 0;
}