快速排序+查找

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 const int maxn=10000;
 7 int f[maxn];
 8 void swap(int &a,int &b){int t=a;a=b;b=t;}
 9 
10 /*********************************************/
11 //所有l均为数组起始下标，所有r均为数组结束下标
12 void quicksort(int a[],int l,int r)//快速排序
13 {
14     if(l<r)
15     {
16         int t=a[l],i=l,j=r;
17         while(i!=j)
18         {
19             while(t<=a[j] && i<j) j--;
20             while(a[i]<=t && i<j) i++;
21             if(i<j) swap(a[i],a[j]);
22         }
23         a[l]=a[i];a[i]=t;
24         quicksort(a,l,i-1);
25         quicksort(a,i+1,r);
26     }
27 }
28 
29 int binary_search(int a[],int l,int r,int val)//二分查找，未找到返回-1
30 {
31     int mid,ans=-1;
32     while(l<=r)
33     {
34         mid=(l+r)>>1;
35         if(val>a[mid]) l=mid+1;
36         else if(val==a[mid]) return mid;
37         else r=mid-1;
38     }
39     return ans;
40 }
41 
42 int lower_bound(int a[],int l,int r,int val)//二分下界查找，无下界返回-1
43 {
44     int mid,ans=-1;
45     while(l<=r)
46     {
47         mid=(l+r)>>1;
48         if(a[mid]<=val) ans=mid,l=mid+1;
49         else r=mid-1;
50     }
51     return ans;
52 }
53 
54 int upper_bound(int a[],int l,int r,int val)//二分上届查找，无上届返回-1
55 {
56     int mid,ans=-1;
57     while(l<=r)
58     {
59         mid=(l+r)>>1;
60         if(a[mid]>=val)  ans=mid,r=mid-1;
61         else l=mid+1;
62     }
63     return ans;
64 }
65 /*********************************************/
66 
67 int main()
68 {
69     int i,n;
70     while(~scanf("%d",&n))
71     {
72         for(i=1;i<=n;i++) scanf("%d",f+i);
73         quicksort(f,1,n);
74         for(i=1;i<=n;i++) printf("%d ",f[i]);
75         puts("");
76         int t,p;
77         puts("5次二分查找");t=5;
78         while(t--){scanf("%d",&p);printf("%d\n",binary_search(f,1,n,p));}
79         puts("5次二分下界查找");t=5;
80         while(t--){scanf("%d",&p);printf("%d\n",lower_bound(f,1,n,p));}
81         puts("5次二分上界查找");t=5;
82         while(t--){scanf("%d",&p);printf("%d\n",upper_bound(f,1,n,p));}
83     }
84     return 0;
85 }