50. 分别使用迭代或递归来实现对数组的二分查找(折半查找)

 

//二分查找,迭代版
#include <stdio.h>

int binarySearch1(int *p,int low,int high,int find)
{
    int mid;
    while(low<=high)//注意点1，当相等时仍需要再进行一次
    {
        mid = (low+high)/2;
        if(p[mid] == find)
            return mid;
        else if(p[mid] < find)
        {
            low = mid+1;
        }
        else if(p[mid] > find)
        {
            high = mid-1;
        }
    }
    return -1;
}


//二分查找，递归版
int binarySearch2(int *p,int low,int high,int find)
{
    int mid;
    if(low<=high)//注意点1，当相等时仍需要再进行一次
    {
        mid = (low+high)/2;
        if(p[mid] == find)
            return mid;
        else if(p[mid] < find)
        {
            return binarySearch2(p,mid+1,high,find);
        }
        else if(p[mid] > find)
        {
            return binarySearch2(p,low,mid-1,find);
        }
    }
    return -1;
}



int main(void)
{
    int arr[10] = {1,15,23,33,45,56,87,91,100,102};

    int idx = binarySearch2(arr,0,9,91);
    if(idx != -1)
    {
        printf("your find idx = %d\n",idx);
    }
    else
        printf("find none\n");



    return 0;
}