我的第35个代码

创建函数利用二分法

#define  _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<math.h>
#include<string.h>

int judge(int arr[], int k)
{
    int length = strlen(arr);
    int left = 1;
    int right = length;
    while (left<=right)
    {
        int mid = (right + left) / 2;
        if (arr[mid - 1] < k)
        {
            left = mid + 1;
        }
        else if (arr[mid - 1 > k])
        {
            right = mid - 1;
        }
        else if (arr[mid - 1] == k)
            return mid - 1;
        else
            return - 1;
    }
}