二分查找--python

import random

# 二分查找--递归实现
def binary_search(arr, left, right, num):
    if left > right:
        return -1
    mid = (left + right) // 2
    if arr[mid] < num:
        left = mid + 1
    elif arr[mid] > num:
        right = mid - 1
    else:
        return mid
    return binary_search(arr, left, right, num)


# 二分查找非递归实现
def binary_chop(arr, data):
    n = len(arr)
    first = 0
    last = n - 1

    while first <= last:
        mid = (last + first) // 2
        if arr[mid] > data:
            last = mid - 1
        elif arr[mid] < data:
            first = mid + 1
        else:
            return mid
    return -1

if __name__ == '__main__':
    arr = [11, 32, 51, 21, 42, 9, 5, 6, 7, 8]
    print(arr)
    arr.sort()
    print(arr)

    num = random.randint(0, 52)
    print('要查找的数:', num)
    res = binary_search(arr, 0, len(arr) - 1, num)
    if -1 == res:
        print('未找到!')
    else:
        print('找到了，索引', res)
    num = arr[random.randint(0, len(arr))]
    print('要查找的数:', num)
    res = binary_search(arr, 0, len(arr) - 1, num)
    if -1 == res:
        print('未找到!')
    else:
        print('找到了，索引', res)

    print('*********************')
    print('二分查找非递归实现')
    num = random.randint(0, 52)
    print('要查找的数:', num)
    res = binary_search(arr, 0, len(arr) - 1, num)
    if -1 == res:
        print('未找到!')
    else:
        print('找到了，索引', res)
    num = arr[random.randint(0, len(arr))]
    print('要查找的数:', num)
    res = binary_search(arr, 0, len(arr) - 1, num)
    if -1 == res:
        print('未找到!')
    else:
        print('找到了，索引', res)