折半查找(c语言)

#include 

int main()
{
    int key, pos, a[100], n, i;              // a[]顺序表
    int Search_Ein(int s[], int n, int key); //折半查找函数声明

    printf("请输入数组元素个数：");
    scanf("%d", &n);                              //表长
    printf("请输入（从小到大）所有数组元素：n"); //有序
    for (i = 0; i < n; i++)
    {
        scanf("%d", &a[i]);
    }

    printf("请输入关键字：");
    scanf("%d", &key);
    pos = Search_Ein(a, n, key);
    if (pos >= 0)
        printf("查找成功！在第%d位！n", pos + 1);
    else
        printf("查找失败！n");
    return 0;
}

int Search_Ein(int s[], int n, int key)
{
    int low, high, mid;
    low = 1;
    high = n; //置区间初值
    while (low <= high)
    {
        mid = (low + high) / 2; //计算中间元素序号
        if (s[mid] == key)      //找到待查元素
            return mid;
        else if (s[mid] > key) //中间元素大于关键字
            high = mid - 1;
        else
            low = mid + 1;
    }
    return -1; //查找失败返回-1
}