二分查找

有序数组，查找某个数据，二分法，时间复杂度O(log2n)

int binary_sort(int arr[], int lenght, int value){    if (arr == NULL || lenght == 0)    {        return -1;    }    int start =0;    int end = lenght -1;    while(start <= end)    {        int mid = start + ((end - start)>>1);        if (value == arr[mid])        {            return mid;        }        else if(value > arr[mid])        {            start = mid + 1;        }        else        {            end = mid - 1;        }    }}