POJ 2376

 #include<iostream>//by chengdacaizi.
 #include<stdio.h>
 #define MAXN 25005
 using namespace std;

 struct Cows
 {
     int begin;
     int end;
 };

 Cows cow[MAXN];

 int compare(const void * i,const void * j);
 int main()
 {
     //freopen("acm.acm","r",stdin);
     int i;
     int j;
     int n;
     int t;
     bool boo;
     int last;
     int max;
     int tem;
     int max_num;
     int result;
     scanf("%d %d",&n,&t);
     for(i = ; i < n; ++ i)
     {
         scanf("%d %d",&cow[i].begin,&cow[i].end);
     }
     qsort(cow,n,sizeof(Cows),compare);
     last = ;
     i = ;
     max = ;
     result = ;
     boo = true;
     while()
     {
         max = -;
         while(cow[i].begin <= last)
         {
             if((tem = cow[i].end - last) > max)
             {
                 max = tem;
                 max_num = i;
             }
             ++ i;
         }
         if(max == -)
         {
         //    cout<<cow[i].begin<<"   000000000000"<<endl;//很巧合的处理，当数组越界的时候，当然，还没有完成，那么自动跳出，cout<<-1；
             boo = false;
             break;
         }
         ++ result;
         if(cow[max_num].end >= t)
         {
             break;
         }
         else
         {
             last = cow[max_num].end + ;
         }
     }
     if(boo)
         cout<<result<<endl;
     else
         cout<<-<<endl;

 }

 int compare(const void * i,const void * j)
 {
     return *((int *)i) - *((int *)j);
 }