ERROR: List indices must be integers or slices, not float in below binary search program in python, please find me a solution

Question

我正在尝试执行二进制搜索程序，但出现错误，错误：列表索引必须是整数或切片，而不是浮点数。请帮忙。

Python 递归二进制搜索程序。

Returns x 在 arr 中的索引（如果存在），否则 -1

def binarySearch (arr, l, r, x): 

# Check base case 
if r >= l: 

    mid = l + (r - l)/2

    # If element is present at the middle itself 
    if arr[mid] == x: 
        return mid 

    # If element is smaller than mid, then it  
    # can only be present in left subarray 
    elif arr[mid] > x: 
        return binarySearch(arr, l, mid-1, x) 

    # Else the element can only be present  
    # in right subarray 
    else: 
        return binarySearch(arr, mid + 1, r, x) 

else: 
    # Element is not present in the array 
    return -1

    # Test array 
arr = [ 2, 3, 4, 10, 40 ] 
x = 10

    # Function call 
result = binarySearch(arr, 0, len(arr)-1, x) 

if result != -1: 
     print("Element is present at index % d" % result )
else: 
     print("Element is not present in array")

Answer 1

您使用的是 Python 3.x，除法结果是浮点数，因此 mid = l + (r - l)/2 中的 mid 实际上是 float ，但随后您尝试执行 arr[mid]，这是一个错误，因为列表不能按浮点数索引。

如果你想要整数除法，这样做：

mid = l + (r - l)//2 # double slash

Answer 2

终于找到了。

在第 6 行，中间 = l + (r - l)/2

改为

mid = l + (r - l)//2

并成功。

ERROR: List indices must be integers or slices, not float in below binary search program in python, please find me a solution

ERROR: List indices must be integers or slices, not float in below binary search program in python, please find me a solution

python

binary-search