# poj 1949 Chores (拓扑排序+dp)

Posted by 111qqz on Wednesday, November 8, 2017

# 思路：

``````/* ***********************************************
Author :111qqz
Created Time :2017年11月07日 星期二 13时52分27秒
File Name :3249.cpp
************************************************ */

#include <iostream>
#include <cmath>
#include <queue>
#include <cstdio>
#include <cstring>
#define PB push_back
#define fst first
#define sec second
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define ms(a,x) memset(a,x,sizeof(a))
typedef long long LL;
#define pi pair < int ,int >
#define MP make_pair

using namespace std;
const double eps = 1E-8;
const int dx4[4]={1,0,0,-1};
const int dy4[4]={0,-1,1,0};
const int inf = 0x3f3f3f3f;
const int N=1E5+7;
vector <int>edge[N];
int in[N],out[N];
int n;
int dp[N];
int val[N];
void init()
{
for ( int i = 0 ; i < N ; i++) edge[i].clear();
ms(in,0);
ms(out,0);
ms(dp,0xca);
//   cout<<"dp:"<<dp[1]<<endl;
}
void topo()
{
queue<int>Q;
for ( int i = 1 ; i <= n ; i++)
if (in[i]==0) Q.push(i),dp[i] = val[i];

while (!Q.empty())
{
int cur = Q.front();
//  cout<<"cur:"<<cur<<endl;
Q.pop();
int siz = edge[cur].size();
for ( int i = 0 ; i < siz ; i++)
{
int v = edge[cur][i];
//      printf("%d->%d val[v]:%d dp[cur]: %d dp[v]:%d ",cur,v,val[v],dp[cur],dp[v]);
dp[v] = max(dp[v],dp[cur]+val[v]);
//      printf("new dp[v]:%d\n",dp[v]);
in[v]--;
if (in[v]==0) Q.push(v);
}
}
}
void pr()
{
for ( int i = 1 ; i <= n ; i++) printf("%d%c",dp[i],i==n?'\n':' ');
}
int main()
{
#ifndef  ONLINE_JUDGE
freopen("./in.txt","r",stdin);
#endif
while (~scanf("%d",&n))
{
init();
for ( int i = 1 ; i <= n ; i++)
{
int x,m;
x = i;
scanf("%d %d",&val[i],&m);
while (m--)
{
int y;
scanf("%d",&y);
//      cout<<"x:"<<x<<" y:"<<y<<endl;
edge[y].PB(x);
out[y]++;
in[x]++;
}
}
topo();
int ans = -inf;
//  pr();
for ( int i = 1 ; i <= n ; i++) if (!out[i]&&dp[i]>ans) ans = dp[i];
printf("%d\n",ans);
}

#ifndef ONLINE_JUDGE
fclose(stdin);
#endif
return 0;
}
``````

「真诚赞赏，手留余香」