1 到10  查找7  一个折半查找法 谢谢了

取左右端点的中间值，如果比预期小（升序下），就更新为左端点，不然就更新为右端点

bsearch(),不谢

#include <stdio.h>

void half(int *a,int left, int right,int num)
{
    if(num == a[left])
    {
        printf("the loc is %d\n",left);
        return;
    }
    if(num == a[right])
    {
        printf("the loc is %d\n",right);
        return;
    }
   
   
    if(num > a[(left+right)/2])
    {
        left = (left+right)/2;
        half(a,left,right,num);
    }
    else if(num <  a[(left+right)/2])
    {
        right = (left+right)/2;
        half(a,left,right,num);
        
    }
    else
    {
        printf("the loc is %d\n",(left+right)/2);
        return;
    }
}
void main()
{
    int a[10] = {1,2,3,4,5,6,7,8,9,10};
    int num = 7;

    half(a,0,9,num);
}

void main()
{
    int a[10] = {1,2,3,4,5,6,7,8,9,10};
    int num = 7;

    half(a,0,9,num);
}

void half(int *p,int min,int max,int num)
{
    int mid;
    mid = (min + max)/2;
    while(min <= max)
    {
        if(num > p[mid])
        {
            min = mid;
            mid = (min + max)/2;
        }
        else if(num < p[mid])
        {
            max = mid;
            mid = (min + max)/2;
        }
        else
        {
        
            break;
        }
    }
    printf("%d\n",mid);
}

#include<stdio.h>
int main()
{
    int array[10]={1,3,5,7,9,11,13,15,17,19};
    int search;
    int l_point=0;                                                     //l_point为左下标，r_point为右下标；
    int r_point=9;
    printf("Input the number you want to search\n");
    scanf("%d",&search);
    if(search==array[r_point])                                         //因为除法是向下取整，因此，若查找的是最后一个数，下标达不到9，此处避免此种情况的死循环；
    {
        printf("Already exists,and it's the %dth number\n",r_point+1);
    }
    else                                                               //同理，若查找的是第一个数，下标可以达到0，此种情况可以放在while循环中；
    {
        while(l_point!=r_point)
        {
           if(search>array[(l_point+r_point)/2])
           {
               l_point=(l_point+r_point)/2;
           }
           else if(search<array[(l_point+r_point)/2])
           {
               r_point=(l_point+r_point)/2;
           }
           else
           {
               break;
           }
        }
          printf("Already exists,and it's the %dth number\n",(l_point+r_point)/2+1);
    }
    return(0);
}