Environment: Python 3.8

Key technique: for, if

There is a function signFunc(x) that returns:

  • -1 if x is negative.
  • 0 if x is equal to 0.

You are given an integer array nums. Let product be the product of all values in the array nums.

Return signFunc(product).

Example 1:

Input: nums = [-1,-2,-3,-4,3,2,1]
Output: 1
Explanation: The product of all values in the array is 144, and signFunc(144) = 1

Analysis:

  1. ans=ans x nums[i] by using loop
  2. if ans >0, return 1
  3. if ans <0, return -1
  4. if ans==0, return 0

Solution:

class Solution:
def arraySign(self, nums):
ans=1
for i in range(len(nums)):
ans=ans*nums[i]
if ans >0:
return 1
if ans <0:
return -1
if ans ==0:
return 0

Submissions:

Environment: Python 3.8

Key technique: if

Given a string s consisting of only the characters 'a' and 'b', return true if every 'a' appears before every 'b' in the string. Otherwise, return false.

Example 1:

Input: s = "aaabbb"
Output: true
Explanation:
The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.
Hence, every 'a' appears before every 'b' and we return true.

Analysis:

  1. If yes, return False. Else, return True.

Solution:

class Solution:
def checkString(self, s):
if "ba" in s:
return False
else:
return True

Submissions:

Environment: Python 3.8

Key technique: str(), int()

Reversing an integer means to reverse all its digits.

Given an integer num, reverse num to get reversed1, then reverse reversed1 to get reversed2. Return true if reversed2 equals num. Otherwise return false.

Example 1:

Input: num = 526
Output: true
Explanation: Reverse num to get 625, then reverse 625 to get 526, which equals num.

Analysis:

  1. Convert it to int format.
  2. Convert it to a string format and reverse it.
  3. If input equal converted result, return pass.
  4. Else, return Fail.

Solution:

class Solution:
def isSameAfterReversals(self, num):
temp=str(num)
temp=int(temp[::-1])
temp=str(temp)
temp=temp[::-1]
if int(temp) ==num:
return True
else:
return False

Submissions:

Environment: Python 3.8

Key technique: for, [::-1]

Given an array of strings words, return the first palindromic string in the array. If there is no such string, return an empty string "".

A string is palindromic if it reads the same forward and backward.

Example 1:

Input: words = ["abc","car","ada","racecar","cool"]
Output: "ada"
Explanation: The first string that is palindromic is "ada".
Note that "racecar" is also palindromic, but it is not the first.

Analysis:

  1. If string == reversed string, return it.
  2. If no string and reversed string is equal, return ‘’

Solution:

class Solution:
def firstPalindrome(self, words):
for i in words:
if i==i[::-1]:
return i
return ''

Submissions:

Reference:

https://leetcode.com/problems/find-first-palindromic-string-in-the-array/discuss/1639462/Python-99-faster-Simple-Solution

Environment: Python 3.8

Key technique: set, if, for

There are n rings and each ring is either red, green, or blue. The rings are distributed across ten rods labeled from 0 to 9.

You are given a string rings of length 2n that describes the n rings that are placed…

Environment: Python 3.8

Key technique: set, list

Given two string arrays words1 and words2, return the number of strings that appear exactly once in each of the two arrays.

Example 1:

Input: words1 = ["leetcode","is","amazing","as","is"], words2 = ["amazing","leetcode","is"]
Output: 2
Explanation:
- "leetcode" appears exactly once in each of the two arrays. We…

Fatboy Slim

Interesting in any computer science.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store