问题陈述

Problem Statement：

You are given a non-negative number in the form of list elements. For example, the number 123 would be provided as arr = [1, 2, 3]. Add one to the number and return the output in the form of a new list.

Example 1: * input = [1, 2, 3] * output = [1, 2, 4]

Example 2: * input = [9, 9, 9] * output = [1, 0, 0, 0]

Challenge:

One way to solve this problem is to convert the input array into a number and then add one to it. For example, if we have input = [1, 2, 3], you could solve this problem by creating the number 123 and then separating the digits of the output number 124.

But can you solve it in some other way?

python实现

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def add_one(input_list):
    if input_list is None:
        return None
    i = len(input_list) - 1
    while i >= 0:
        if input_list[i] != 9:
            input_list[i] += 1
            return input_list
        elif input_list[i] == 9:
            input_list[i] = 0
            i -= 1
    input_list.insert(0, 1)
    return input_list

测试用例： 

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def test_function(test_case):
    arr = test_case[0]
    solution = test_case[1]
    
    output = add_one(arr)
    for index, element in enumerate(output):
        if element != solution[index]:
            print("Fail")
            return
    print("Pass")  

arr = [0]
solution = [1]
test_case = [arr, solution]
test_function(test_case)

arr = [1, 2, 3]
solution = [1, 2, 4]
test_case = [arr, solution]
test_function(test_case)

arr = [9, 9, 9]
solution = [1, 0, 0, 0]
test_case = [arr, solution]
test_function(test_case)