POJ 1201 Intervals

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 50010;
18 struct arc{
19     int to,w,next;
20     arc(int x = 0,int y = 0,int z = 0){
21         to = x;
22         w = y;
23         next = z;
24     }
25 };
26 int n,tot,head[maxn],theMin,theMax,d[maxn];
27 arc e[maxn<<2];
28 int q[maxn<<4],he,tail;
29 bool in[maxn];
30 void add(int u,int v,int w){
31     e[tot] = arc(v,w,head[u]);
32     head[u] = tot++;
33 }
34 int spfa(){
35     for(int i = theMin; i <= theMax; i++){
36         in[i] = false;
37         d[i] = -INF;
38     }
39     d[theMin] = 0;
40     he = tail = 0;
41     q[tail++] = theMin;
42     while(he < tail){
43         int u = q[he++];
44         in[u] = false;
45         for(int i = head[u]; ~i; i = e[i].next){
46             if(d[e[i].to] < d[u]+e[i].w){
47                 d[e[i].to] = d[u]+e[i].w;
48                 if(!in[e[i].to]){
49                     in[e[i].to] = true;
50                     q[tail++] = e[i].to;
51                 }
52             }
53         }
54     }
55     return d[theMax];
56 }
57 int main() {
58     int u,v,w;
59     while(~scanf("%d",&n)){
60         memset(head,-1,sizeof(head));
61         theMin = INF;
62         theMax = -INF;
63         for(int i = tot = 0; i < n; i++){
64             scanf("%d %d %d",&u,&v,&w);
65             add(u,v+1,w);
66             theMin = min(theMin,u);
67             theMax = max(theMax,v+1);
68         }
69         for(int i = theMin; i < theMax; i++){
70             add(i,i+1,0);
71             add(i+1,i,-1);
72         }
73         printf("%d\n",spfa());
74     }
75     return 0;
76 }