折半查找,快速排序

#include <stdio.h>
#define MAX 100
void qsort(int a[],int p,int r);
int Partition(int a[],int p,int r);
int search(int a[],int key,int p,int r);
int main()
{
    int n,i,key,b;
    printf("input the number of elements\n");
    scanf("%d",&n);
    int a[MAX];
    printf("input elements\n");
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=1;i<=n;i++)
    {
        printf("%d ",a[i]);
    }
    printf("\n");
    qsort(a,1,n);
    for(i=1;i<=n;i++)
    {
        printf("%d ",a[i]);
    }
    printf("\n");
    printf("input the key word you want to check!\n");
    scanf("%d",&key);
    b=search(a,key,1,n);
    printf("%d\n",b);


    return 0;
}
void qsort(int a[],int p,int r)
{
    int q;
    if(p<r)
    {
        q=Partition(a,p,r);
        qsort(a,p,q-1);
        qsort(a,q+1,r);
    }
}
int Partition(int a[],int p,int r)
{
    int key=a[p];
    while(p<r)
    {
        while(p<r&&a[r]>key)
            r--;
        a[p]=a[r];
        while(p<r&&a[p]<key)
            p++;
        a[r]=a[p];
    }
    a[p]=key;
    return p;
}
int search(int a[],int key,int p,int r)
{
    int mid=0;
    while(p<r)
    {
        mid=(p+r)/2;
        if(a[mid]>key)
            r=mid-1;
        else if(a[mid]<key)
            p=mid+1;
        else
            return mid;
    }
    return mid;
}