快速排序+查找

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int maxn=10000;
int f[maxn];
void swap(int &a,int &b){int t=a;a=b;b=t;}

/*********************************************/
//所有l均为数组起始下标，所有r均为数组结束下标
void quicksort(int a[],int l,int r)//快速排序
{
    if(l<r)
    {
        int t=a[l],i=l,j=r;
        while(i!=j)
        {
            while(t<=a[j] && i<j) j--;
            while(a[i]<=t && i<j) i++;
            if(i<j) swap(a[i],a[j]);
        }
        a[l]=a[i];a[i]=t;
        quicksort(a,l,i-1);
        quicksort(a,i+1,r);
    }
}

int binary_search(int a[],int l,int r,int val)//二分查找，未找到返回-1
{
    int mid,ans=-1;
    while(l<=r)
    {
        mid=(l+r)>>1;
        if(val>a[mid]) l=mid+1;
        else if(val==a[mid]) return mid;
        else r=mid-1;
    }
    return ans;
}

int lower_bound(int a[],int l,int r,int val)//二分下界查找，无下界返回-1
{
    int mid,ans=-1;
    while(l<=r)
    {
        mid=(l+r)>>1;
        if(a[mid]<=val) ans=mid,l=mid+1;
        else r=mid-1;
    }
    return ans;
}

int upper_bound(int a[],int l,int r,int val)//二分上届查找，无上届返回-1
{
    int mid,ans=-1;
    while(l<=r)
    {
        mid=(l+r)>>1;
        if(a[mid]>=val)  ans=mid,r=mid-1;
        else l=mid+1;
    }
    return ans;
}
/*********************************************/

int main()
{
    int i,n;
    while(~scanf("%d",&n))
    {
        for(i=1;i<=n;i++) scanf("%d",f+i);
        quicksort(f,1,n);
        for(i=1;i<=n;i++) printf("%d ",f[i]);
        puts("");
        int t,p;
        puts("5次二分查找");t=5;
        while(t--){scanf("%d",&p);printf("%d\n",binary_search(f,1,n,p));}
        puts("5次二分下界查找");t=5;
        while(t--){scanf("%d",&p);printf("%d\n",lower_bound(f,1,n,p));}
        puts("5次二分上界查找");t=5;
        while(t--){scanf("%d",&p);printf("%d\n",upper_bound(f,1,n,p));}
    }
    return 0;
}