Binarysearch basic binary search

ac Implementation code ：

Position BinarySearch( List L, ElementType X )
{
    int left=1,right=L->Last,mid=(left+right)/2;
    while(left<=right)
    {
        if(L->Data[mid]>X)
        {
            right=mid-1;
        }
        else if(L->Data[mid]<X)
        {
            left=mid+1;
        }
        else if(L->Data[mid]==X)
        {
            return mid;
        }
        mid=(left+right)/2;
    }
    return NotFound;
}

details ：

        left<=right Cannot be less than , Otherwise, even number , After finding it in the middle , Unable to enter the loop , Leakage .