BZOJ1689: [Usaco2005 Open] Muddy roads

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<cstdlib>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<iostream>
 7 using namespace std;
 8 int n,L;
 9 struct ken{int l,r;} a[10002];
10 bool kp(const ken &i,const ken &j) {return i.l<j.l;}
11 void init()
12 {
13     scanf("%d%d",&n,&L);
14     int i;
15     for(i=1;i<=n;i++)
16        scanf("%d%d",&a[i].l,&a[i].r);
17     sort(a+1,a+n+1,kp);
18 }
19 void work()
20 {
21     int i,len=0,w=0,ans=0;
22     for(i=1;i<=n;i++)
23        {if(w>=a[i].r) continue;
24         w=max(a[i].l,w);
25         while(w<a[i].r) {ans++; w+=L;}
26        }
27     printf("%d\n",ans);
28 }
29 int main()
30 {
31     init(); work();
32     return 0;
33 }