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Posts tagged as “easy”

่Šฑ่Šฑ้…ฑ LeetCode 1837. Sum of Digits in Base K

By zxi on April 25, 2021

Given an integer n (in base 10) and a base k, return the sum of the digits of n after converting n from base 10 to base k.

After converting, each digit should be interpreted as a base 10 number, and the sum should be returned in base 10.

Example 1:

Input: n = 34, k = 6
Output: 9
Explanation: 34 (base 10) expressed in base 6 is 54. 5 + 4 = 9.

Example 2:

Input: n = 10, k = 10
Output: 1
Explanation: n is already in base 10. 1 + 0 = 1.

Constraints:

  • 1 <= n <= 100
  • 2 <= k <= 10

Solution: Base Conversion

Time complexity: O(logn)
Space complexity: O(1)

C++

่Šฑ่Šฑ้…ฑ LeetCode 1832. Check if the Sentence Is Pangram

By zxi on April 18, 2021

A pangram is a sentence where every letter of the English alphabet appears at least once.

Given a string sentence containing only lowercase English letters, returntrue if sentence is a pangram, or false otherwise.

Example 1:

Input: sentence = "thequickbrownfoxjumpsoverthelazydog"
Output: true
Explanation: sentence contains at least one of every letter of the English alphabet.

Example 2:

Input: sentence = "leetcode"
Output: false

Constraints:

  • 1 <= sentence.length <= 1000
  • sentence consists of lowercase English letters.

Solution: Hashset

Time complexity: O(n)
Space complexity: O(26)

C++

Python3

่Šฑ่Šฑ้…ฑ LeetCode 1827. Minimum Operations to Make the Array Increasing

By zxi on April 17, 2021

You are given an integer array nums (0-indexed). In one operation, you can choose an element of the array and increment it by 1.

  • For example, if nums = [1,2,3], you can choose to increment nums[1] to make nums = [1,3,3].

Return the minimum number of operations needed to make nums strictly increasing.

An array nums is strictly increasing if nums[i] < nums[i+1] for all 0 <= i < nums.length - 1. An array of length 1 is trivially strictly increasing.

Example 1:

Input: nums = [1,1,1]
Output: 3
Explanation: You can do the following operations:
1) Increment nums[2], so nums becomes [1,1,2].
2) Increment nums[1], so nums becomes [1,2,2].
3) Increment nums[2], so nums becomes [1,2,3].

Example 2:

Input: nums = [1,5,2,4,1]
Output: 14

Example 3:

Input: nums = [8]
Output: 0

Constraints:

  • 1 <= nums.length <= 5000
  • 1 <= nums[i] <= 104

Solution: Track Last

Time complexity: O(n)
Space complexity: O(1)

C++

่Šฑ่Šฑ้…ฑ LeetCode 1822. Sign of the Product of an Array

By zxi on April 12, 2021

There is a function signFunc(x) that returns:

  • 1 if x is positive.
  • -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

Example 2:

Input: nums = [1,5,0,2,-3]
Output: 0
Explanation: The product of all values in the array is 0, and signFunc(0) = 0

Example 3:

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

Constraints:

  • 1 <= nums.length <= 1000
  • -100 <= nums[i] <= 100

Solution: Sign Only

No need to compute the product, only track the sign changes. Flip the sign when encounter a negative number, return 0 if there is any 0 in the array.

Time complexity: O(n)
Space complexity: O(1)

C++

่Šฑ่Šฑ้…ฑ LeetCode 1816. Truncate Sentence

By zxi on April 6, 2021

A sentence is a list of words that are separated by a single space with no leading or trailing spaces. Each of the words consists of only uppercase and lowercase English letters (no punctuation).

  • For example, "Hello World", "HELLO", and "hello world hello world" are all sentences.

You are given a sentence sโ€‹โ€‹โ€‹โ€‹โ€‹โ€‹ and an integer kโ€‹โ€‹โ€‹โ€‹โ€‹โ€‹. You want to truncate sโ€‹โ€‹โ€‹โ€‹โ€‹โ€‹ such that it contains only the first kโ€‹โ€‹โ€‹โ€‹โ€‹โ€‹ words. Return sโ€‹โ€‹โ€‹โ€‹โ€‹โ€‹ after truncating it.

Example 1:

Input: s = "Hello how are you Contestant", k = 4
Output: "Hello how are you"
Explanation:
The words in s are ["Hello", "how" "are", "you", "Contestant"].
The first 4 words are ["Hello", "how", "are", "you"].
Hence, you should return "Hello how are you".

Example 2:

Input: s = "What is the solution to this problem", k = 4
Output: "What is the solution"
Explanation:
The words in s are ["What", "is" "the", "solution", "to", "this", "problem"].
The first 4 words are ["What", "is", "the", "solution"].
Hence, you should return "What is the solution".

Example 3:

Input: s = "chopper is not a tanuki", k = 5
Output: "chopper is not a tanuki"

Constraints:

  • 1 <= s.length <= 500
  • k is in the range [1, the number of words in s].
  • s consist of only lowercase and uppercase English letters and spaces.
  • The words in s are separated by a single space.
  • There are no leading or trailing spaces.

Solution:

Time complexity: O(n)
Space complexity: O(n)

C++

Python3