POJ 3249 Test for Job

POJ 3249 Test for Job

dfs DAG最长路

题意

思路

代码

#include <cstdio>
#include <cstdlib>
//#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <cmath>
#include <queue>
#include <stack>
#include <map>

//#define _ ios_base::sync_with_stdio(0),cin.tie(0)
#define M(a,b) memset(a,b,sizeof(a))
using namespace std;

const int MAXN=100005;
const int oo=0x3f3f3f3f;
typedef long long LL;
const LL loo=4223372036854775807ll;
typedef long double LB;
const LL mod=1e9+7;

int val[MAXN];
vector<int> G[MAXN];
LL res[MAXN];
LL dfs(int n)
{
if(res
!=-loo) return res
;
if(G
.size()==0) return res
=val
;

for(int i=0;i<G
.size();i++)
{
int t=G
[i];
res
=max(res
, (LL)val
+dfs(t));
}
return res
;
}
int indegree[MAXN];
int main()
{
//_;
int n;
while(scanf("%d",&n)==1)
{
for(int i=0;i<MAXN;i++) G[i].clear();
M(indegree, 0);
int e=0;
for(int i=0;i<MAXN;i++) res[i]=-loo;
int m;scanf("%d", &m);
for(int i=1;i<=n;i++) scanf("%d", &(val[i]));
for(int i=0;i<m;i++)
{
int a, b;scanf("%d%d", &a, &b);
G[a].push_back(b);

indegree[b]++;
}
LL ttt=-loo;
for(int i=1;i<=n;i++)
{
if(indegree[i]==0)
ttt=max(ttt, dfs(i));
}
printf("%lld\n", ttt);
}
return 0;
}