二分查詢的遞迴實現

#include <stdio.h>
#include <assert.h>
int  BinarySearchR(int* a,int n,int left,int right,int key) 
{
    assert(a&&n>0);
    assert(left >= 0);
    assert(right < n);
//傳入引數判斷
    int mid = (left + right) >> 1;
    if (left < right)
        return -1;  //如果沒找到返回-1
 

    if (a[mid] == key)
        return mid;  //找到了就返回下標
    else if (a[mid] < key)
       return BinarySearchR(a,n, mid + 1, right, key);
    else if (a[mid]>key)
       return BinarySearchR(a,n, left, mid-1, key);
}
int main()
{
    int a[] = { 1, 2, 3, 5, 6, 8, 15, 17, 20 };
    printf("%d", BinarySearchR(a, (sizeof
 
(a) / sizeof(a[0])), 0, (sizeof(a) / sizeof(a[0])) - 1, 16));

    return 0;
}