最大不相交区间数+最少区间数覆盖问题 贪心思想

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef unsigned int ui;
 4 typedef long long ll;
 5 typedef unsigned long long ull;
 6 #define pf printf
 7 #define mem(a,b) memset(a,b,sizeof(a))
 8 #define prime1 1e9+7
 9 #define prime2 1e9+9
10 #define pi 3.14159265
11 #define lson l,mid,rt<<1
12 #define rson mid+1,r,rt<<1|1
13 #define scand(x) scanf("%llf",&x) 
14 #define f(i,a,b) for(int i=a;i<=b;i++)
15 #define scan(a) scanf("%d",&a)
16 #define mp(a,b) make_pair((a),(b))
17 #define P pair<int,int>
18 #define dbg(args) cout<<#args<<":"<<args<<endl;
19 #define inf 0x7ffffff
20 inline int read(){
21     int ans=0,w=1;
22     char ch=getchar();
23     while(!isdigit(ch)){if(ch==‘-‘)w=-1;ch=getchar();}
24     while(isdigit(ch))ans=(ans<<3)+(ans<<1)+ch-‘0‘,ch=getchar();
25     return ans*w;
26 }
27 int n,m,t;
28 const int maxn=1e4+10;
29 struct node{
30     int l,r;
31 }p[maxn];
32 bool cmp(node& a,node& b)
33 {
34     return a.r<b.r;
35 } 
36 int main()
37 {
38     //freopen("input.txt","r",stdin);
39     //freopen("output.txt","w",stdout);
40     std::ios::sync_with_stdio(false);
41     while(scanf("%d",&n)&&n)
42     {
43         f(i,1,n)
44         {
45             p[i].l=read(),p[i].r=read();
46         }
47         p[0].r=0;
48         sort(p+1,p+n+1,cmp);
49         int ans=0;
50         int last=0;
51         f(i,1,n)
52         {
53             if(p[i].l>=last)
54             {
55                 ans++;
56                 last=p[i].r;    
57             }
58         }
59         pf("%d\n",ans);
60     }
61 }