poj 1192最优连通子集（简单树形dp）

题目链接：http://poj.org/problem?id=1192

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;

const int maxn = 1005;
const int INF = 0x3f3f3f;

int dp[maxn];
vector<int> G[maxn];
int W[maxn];
int N;
struct Point{
    int x,y;
}P[maxn];
int ans;

void dfs(int u,int fa){
    dp[u] = W[u];
    for(int i=0;i<G[u].size();i++){
        int v = G[u][i];
        if(v == fa) continue;
        dfs(v,u);
        dp[u] += max(dp[v],0);
    }
    ans = max(ans,dp[u]);
}

int main()
{
   // freopen("E:\\acm\\input.txt","r",stdin);
    scanf("%d",&N);
    for(int i=1;i<=N;i++){
        scanf("%d %d",&P[i].x,&P[i].y);
        scanf("%d",&W[i]);
    }
    for(int i=1;i<=N;i++)
        for(int j=i+1;j<=N;j++)
            if(abs(P[i].x-P[j].x) + abs(P[i].y-P[j].y) == 1){
                G[i].push_back(j);
                G[j].push_back(i);
            }

    ans = -INF;
    dfs(1,-1);
    printf("%d\n",ans);
}