hdu 1011 Starship Troopers

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

　　入门级树dp，这题就是要注意一下输入的时候要特判一个m为0的情况。

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <vector>
#include <algorithm>

using namespace std;

const int maxn = 105;

int dp[maxn][maxn];
bool vis[maxn];
int p[maxn], b[maxn];
vector<int> nd[maxn];

int max2(int x, int y){return (x > y) ? x : y;}

void init(int n, int m){
    for (int i = 1; i <= n; i++){
        vis[i] = false;
        p[i] = b[i] = 0;
        nd[i].clear();
    }
    memset(dp, 0, sizeof(dp));
}

bool data(int &n, int &m){
    scanf("%d%d", &n, &m);
    if (n == -1 && m == -1) return false;
    init(n, m);
    for (int i = 1; i <= n; i++){
        scanf("%d%d", &b[i], &p[i]);
    }
    for (int i = 1, x, y; i < n; i++){
        scanf("%d%d", &x, &y);
        nd[x].push_back(y);
        nd[y].push_back(x);
    }
    return true;
}

void dfs(int m, int rt){
    vis[rt] = true;
    int bg = (b[rt] + 19) / 20;

    for (int i = bg; i <= m; i++)
        dp[rt][i] = p[rt];
    if (bg <= m && !nd[rt].size()){
        return ;
    }
    for (int i = 0; i < nd[rt].size(); i++){
        if (vis[nd[rt][i]]) continue;
        dfs(m, nd[rt][i]);
        for (int j = m; j >= bg; j--){
            for (int k = 1; k <= j - bg; k++){
                dp[rt][j] = max2(dp[rt][j - k] + dp[nd[rt][i]][k], dp[rt][j]);
            }
        }
    }
}

int main(){
    int n, m;

    while (true){
        if (!data(n, m)) return 0;
        if (!m){
            printf("0\n");
            continue;
        }
        dfs(m, 1);
        printf("%d\n", dp[1][m]);
    }
}

——written by  Lyon