Lunski's Clutter

Given a 32-bit signed integer, reverse digits of an integer.

Note: Assume we are dealing with an environment that could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For this problem, assume that your function returns 0 when the reversed integer overflows.

Example 1:

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Input: x = 123
Output: 321

Example 2:

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Input: x = -123
Output: -321

Example 3:

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Input: x = 120
Output: 21

Example 4:

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Input: x = 0
Output: 0

Constraints:

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-2ˆ31 <= x <= 231 - 1

上次跟大家提到重訓的吃，接下來就是開始動，問題是怎麼動呢？ 其實我一開始也不知道，所以這份課表叫十里坡，在不斷努力後，還是練成了劍神。

Given an integer n, return true if it is a power of three. Otherwise, return false.

An integer n is a power of three, if there exists an integer x such that n == 3x.

Example 1:

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Input: n = 27
Output: true

Example 2:

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Input: n = 0
Output: false

Example 3:

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Input: n = 9
Output: true

Example 4:

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Input: n = 45
Output: false

Given a non-empty array of decimal digits representing a non-negative integer, increment one to the integer.

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contains a single digit.

You may assume the integer does not contain any leading zero, except the number 0 itself.

Example 1:

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Input: digits = [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.

Example 2:

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Input: digits = [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

Example 3:

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Input: digits = [0]
Output: [1]