執行結果：

程式碼如下：

#include<stdio.h>
//陣列初始化函式
void Array_get(int array[],int max)
{
    printf("請輸入一個數組，大小從低到高，各個數字間以空格隔開：");
    for (size_t i = 0; i < max; i++)
    {
        scanf("%d",&array[i]);
    }
}
//折半查詢
int bin_search(int array[] , int max , int key)
{
    int mid;
    int low = 0; 
    int high = max-1;
    while (low<=high)
    {
        mid = (high-1+low)/2;
        if (key<array[mid])
        {
            high = mid-1;
        }else if (key>array[mid])
        {
            low = mid+1;
        }else if (key==array[mid])
        {
            return mid;
        }
    }
}
int main()
{
    int max,key;
    printf("請輸入陣列元素個數：");
    scanf("%d",&max);
    int array[max];
    Array_get(array,max);
    printf("請輸入要查詢的數字：");
    scanf("%d",&key);
    printf("%d在第%d位",key,bin_search(array,max,key)+1);
    return 0;
}