二分查找----第一种（相同元素返回不确定哪个）

/*
 *binary search 
 *just return a value position equals the find but may not the first one
 *we should caution the left open right close or left close and right close rules to not happen the boundary error
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*
 *binary search
 *return -1 can not find the number else the position of the number
 */

int binary_search(int in_arr[],int n,int value)
{
    int left,right,middle;
    left = 0,right = n - 1;

    while(left <= right)
    {
        middle = left + (right - left) / 2; //can solve the number overflow error
        
        if(value > in_arr[middle])
        {
            left = middle + 1;
        }
        else if(value < in_arr[middle])
        {
            right = middle - 1;
        }
        else
        {
            return middle;
        }
    }

    return -1;
}

int main()
{
    int i,value,in_arr[10];

    for(i = 0; i < 10; i++)
    {
        scanf("%d",&in_arr[i]);
    }
    
    while(1)
    {
        printf("input the value to find
");

        scanf("%d",&value);

        int index = binary_search(in_arr,10,value);

        if(index == -1)
        {
            printf("can not find the number %d 
",value);
        }
        else
        {
            printf("the value %d is at the position %d
",value,index);
        }
    }
}