POJ2376 Cleaning Shifts

 1 /*by SilverN*/
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<algorithm>
 7 using namespace std;
 8 const int mxn=1000200;
 9 int n,t;
10 int mx[mxn];//起点是mx[]的区间中，最远的右端点位置
11 int ans=0;
12 int main(){
13     scanf("%d%d",&n,&t);
14     int a,b;
15     int i,j;
16     for(i=1;i<=n;i++){
17         scanf("%d%d",&a,&b);
18         mx[a]=max(mx[a],b);
19     }
20     int last=1,now=1;
21     int ed;
22     while(now<=t){ //now是当前已经覆盖的长度
23         ed=0;
24         for(i=last;i<=now;i++){
25             if(mx[i]>ed){
26                 ed=mx[i];last=i;
27             }
28         }
29         if(ed+1==now){
30             printf("-1\n");
31             return 0;
32         }
33         now=ed+1;ans++;
34         if(ed>=t)break;
35     }
36     if(ed>=t)printf("%d\n",ans);
37     else printf("-1\n");
38     return 0;
39 }
40 /*
41 const int mxn=26000;
42 struct line{
43     int l,r;
44 }a[mxn];
45 int cmp(const line a,const line b){
46     if(a.l!=b.l)return a.l<b.l;
47     return a.r<b.r;
48 }
49 int st,ed;
50 int n,t;
51 int main(){
52     int i,j;
53     scanf("%d%d",&n,&t);
54     for(i=1;i<=n;i++)
55         scanf("%d%d",&a[i].l,&a[i].r);
56     sort(a+1,a+n+1,cmp);
57     ed=0;
58     int ans=0;
59     if(a[1].l<=1)
60     for(i=1;i<=n;i++){
61         int nxt=0;
62         while(i+1<=n && a[i+1].l<=ed+1){
63             i++;
64             nxt=max(nxt,a[i].r);
65         }
66         if(a[i].l<=ed+1) nxt=max(nxt,a[i].r);
67         if(nxt>ed){
68             ed=nxt;
69             ans++;
70         }
71         if(ed>=t)break;
72     }
73     if(ed>=t)printf("%d\n",ans);
74     else printf("-1\n");
75     return 0;
76 }*/