poj 2376 Cleaning Shifts

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<algorithm>
 4 using namespace std;
 5 int vis[1100009];
 6 int a,b;
 7 struct node
 8 {
 9     int a;
10     int b;
11 } d[25500];
12 int dig(int x,int y,int z)
13 {
14     int p=0,q=0,n=-10000;
15     if(y>=b)
16         return z;
17     for(int i=x; i<=a; i++)
18     {
19         if(!vis[i])
20             if(d[i].a<=y+1)
21             {
22                 vis[i]=1;
23                 p=1;
24                 if(d[i].b>=y+1)
25                     if(d[i].b>n)
26                     {
27                         q=i;
28                         n=d[i].b;
29                     }
30             }
31     }
32     if(p==0)
33         return -1;
34     dig(q,n,z+1);
35 }
36 int cmp(struct node a,struct node b)
37 {
38     if(a.a==b.a)
39         return a.b<b.b;
40     return a.a<b.a;
41 }
42 int main()
43 {
44     int i,j;
45     while(scanf("%d%d",&a,&b)!=EOF)
46     {
47         int flag=0;
48         memset(vis,0,sizeof(vis));
49         for(i=1; i<=a; i++)
50         {
51             int t;
52             scanf("%d%d",&d[i].a,&d[i].b);
53             if(d[i].a==1)
54             flag=1;
55         }
56         sort(d+1,d+a+1,cmp);
57         if(flag==0)
58         printf("-1\n");
59         else
60         printf("%d\n",dig(1,d[1].b,1));
61     }
62 }