JZ High School OJ 1382. Interval

Time Limits:  1000 ms  Memory Limits: 65536 KB  Detailed Limits  

Description

　　Alice received some very special birthday gift: interval. Even if it is boring, Alice was able to come up with a lot of games on intervals, one of which is, Alice longest sequence selected from different sections, where each section must meet the gift, the other in the sequence must contain at each interval an interval.
　　Program calculated maximum length sequence.

 

Input

　　The first line of the input file contains an integer N (1 <= N <= 100000), indicates the number of sections.
　　Next N lines of two integers A and B depict a section (1 <= A <= B <= 1000000).

Output

　　The maximum length sequence output condition satisfied.

 

Sample Input

Input 1: 
3 
3. 4 
2. 5 
1. 6 

Input 2: 
. 5 
10 30 
20 is 40 
30 50 
10 60 
30 40 

Input 3: 
. 6 
1. 4 
1. 5 
1. 6 
1. 7 
2. 5 
3. 5

Sample Output

Output 1: 
3 

Output 2: 
3 

Output 3: 
5

 

Data Constraint

 

 

Hint

[Explain] Sample
　　Example 3 can be found in sequence interval length is 5: [1,7], [1,6], [1,5], [2,5], [3,5]

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int MAXN=1e5+5;
 4 const int INF=2e9;
 5 struct node {
 6     int l,r;
 7 }a[MAXN];
 8 int n;
 9 int s[MAXN],top;
10 bool cmp (node a,node b){
11     if (a.l==b.l) return a.r<b.r;
12     return a.l>b.l;
13 }
14 int main(){
15     cin>>n;
16     for (int i=1;i<=n;i++){
17         scanf ("%d%d",&a[i].l,&a[i].r);
18     }
19     sort (a+1,a+n+1,cmp);
20     for (int i=1;i<=n;i++){
21         int t=a[i].r;
22         if (t>=s[top]) s[++top]=t;
23         else {
24             int l=1,r=top,mid;
25             while (l<=r){
26                 mid=(l+r)/2;
27                 if (s[mid]<=t) l=mid+1;
28                 else r=mid-1;
29             }
30             s[l]=t;
31         }
32     }
33     cout<<top<<endl;
34     return 0;
35 }