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则递推： dp(root, 0)  =  西格玛 max(dp(e(root, i),  1) + dp(e(root, i), o))

                 dp(root, 1)  = a[root] + 西格玛(dp(e(root, i), 0)).

#include<cstdio>
#include<cmath>
#include<stdlib.h>
#include<map>
#include<set>
#include<time.h>
#include<vector>
#include<queue>
#include<string>
#include<string.h>
#include<iostream>
#include<algorithm>
using namespace std;
#define eps 1e-8
#define INF 0x3f3f3f3f
#define max(a,b) ((a)>(b)?(a):(b))
#define min(a,b) ((a)<(b)?(a):(b))

#define maxn 6000 + 10
int n, a[maxn], head[maxn], tot;
int dp[maxn][2];

struct edge
{
    int v, next;
}e[maxn*maxn];

void init()
{
    tot = 0;
    memset(head, -1, (n+2)*sizeof(int));
    memset(dp, -1, sizeof(dp));
}

void adde(int u, int v)
{
    e[tot].v = v; e[tot].next = head[u]; head[u] = tot++;
}

void dfs(int u, int fa)
{
    int M0, M1;
    M0 = 0;
    M1 = a[u];
    for(int i=head[u]; i!=-1; i=e[i].next)
    {
        int v = e[i].v;
        if(v == fa) continue;
        dfs(v, u);
        M0 += max(dp[v][0], dp[v][1]);
        M1 += dp[v][0];
    }
    dp[u][0] = M0;
    dp[u][1] = M1;
}

int main()
{
    while(~scanf("%d", &n))
    {
        init();
        for(int i=1; i<=n; i++)
           scanf("%d", &a[i]);
        int u, v;
        while(scanf("%d%d", &u, &v) && u + v)
        {
            adde(u, v);
            adde(v, u);
        }
        dfs(1, -1);
        printf("%d\n", max(dp[1][0], dp[1][1]));
    }
    return 0;
}

HDU 1520

标签：acm   hdu   

原文地址：http://blog.csdn.net/dojintian/article/details/47102003