POJ1201 Intervals

 1 /**/
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<algorithm>
 7 #include<queue>
 8 using namespace std;
 9 const int INF=0x3f3f3f3f;
10 const int mxn=60000;
11 struct edge{
12     int v,dis;
13     int next;
14 }e[mxn*10];
15 int hd[mxn],cnt;
16 int dis[mxn];
17 int vis[mxn];
18 int inq[mxn];
19 int n;
20 void add_edge(int u,int v,int w){
21     e[++cnt].next=hd[u];e[cnt].v=v;e[cnt].dis=w;hd[u]=cnt;
22 }
23 bool SPFA(){
24     memset(dis,-1,sizeof dis);
25     queue<int>q;
26     q.push(0);
27     inq[0]=1;
28     vis[0]=1;
29     dis[0]=0;
30     while(!q.empty()){
31         int u=q.front();
32         for(int i=hd[u];i;i=e[i].next){
33             int v=e[i].v;
34             if(dis[u]+e[i].dis>dis[v]){
35                 dis[v]=dis[u]+e[i].dis;
36                 vis[v]++;
37                 if(vis[v]>n)return 0;
38                 if(!inq[v]){
39                     inq[v]=1;
40                     q.push(v);
41                 }
42             }
43         }
44         q.pop();
45         inq[u]=0;
46     }
47     return 1;
48 }
49 int main(){
50     scanf("%d",&n);
51     int i,j;
52     int mx=-1,a,b,c;
53     for(i=1;i<=n;i++){
54         scanf("%d%d%d",&a,&b,&c);
55         add_edge(a,b+1,c);
56         mx=max(mx,b+1);
57     }
58     for(i=0;i<mx;i++){
59         add_edge(i,i+1,0);
60         add_edge(i+1,i,-1);
61     }
62     SPFA();
63     printf("%d\n",dis[mx]);
64     return 0;
65 }