https://github.com/neckerfree/patternsforcoding
Validate and master some common patterns solving code challenges.
https://github.com/neckerfree/patternsforcoding
Last synced: about 2 months ago
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Validate and master some common patterns solving code challenges.
- Host: GitHub
- URL: https://github.com/neckerfree/patternsforcoding
- Owner: NeckerFree
- Created: 2023-04-21T21:28:16.000Z (about 3 years ago)
- Default Branch: dev
- Last Pushed: 2023-05-21T04:33:08.000Z (about 3 years ago)
- Last Synced: 2025-03-17T15:57:51.548Z (about 1 year ago)
- Language: C#
- Size: 2.92 MB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
> Validate and master some common patterns solving code challenges.
> Exercise 1
Pair with Target Sum
Problem Statement
Given an array of numbers sorted in ascending order and a target sum, find a pair in the array whose sum is equal to the given target.
Write a function to return the indices of the two numbers (i.e. the pair) such that they add up to the given target.
Example 1:
Input: [1, 2, 3, 4, 6], target=6
Output: [1, 3]
Explanation: The numbers at index 1 and 3 add up to 6: 2+4=6
Example 2:
Input: [2, 5, 9, 11], target=11
Output: [0, 2]
Explanation: The numbers at index 0 and 2 add up to 11: 2+9=11
> Exercise 2
Dutch National Flag Problem (medium)
Problem Statement
Given an array containing 0s, 1s and 2s, sort the array in-place. You should treat numbers of the array as objects,
hence, we can’t count 0s, 1s, and 2s to recreate the array.
The flag of the Netherlands consists of three colors: red, white and blue; and since our input array also
consists of three different numbers that is why it is called Dutch National Flag problem.
Example 1:
Input: [1, 0, 2, 1, 0]
Output: [0 0 1 1 2]
Example 2:
Input: [2, 2, 0, 1, 2, 0]
Output: [0 0 1 2 2 2 ]
> Exercise 3
Given an array arr of unsorted numbers and a target sum, count all triplets in it such that arr[i] + arr[j] + arr[k] < target
where i, j, and k are three different indices. Write a function to return the count of such triplets.
Example 1:
Input: [-1, 0, 2, 3], target=3
Output: 2
Explanation: There are two triplets whose sum is less than the target: [-1, 0, 3], [-1, 0, 2]
Example 2:
Input: [-1, 4, 2, 1, 3], target=5
Output: 4
Explanation: There are four triplets whose sum is less than the target: [-1, 4, 1],[-1, 2, 1],[-1, 1, 3],[ -1, 2, 3]
> Exercise 3
Given a 2D array (i.e., a matrix) containing only 1s (land) and 0s (water), count the number of islands in it.
An island is a connected set of 1s (land) and is surrounded by either an edge or 0s (water).
Each cell is considered connected to other cells horizontally or vertically (not diagonally).
> Exercise 4
Given a list of intervals, merge all the overlapping intervals to produce a list that has only mutually exclusive intervals.
Example 1:
Intervals: [[1,4], [2,5], [7,9]]
Output: [[1,5], [7,9]]
Explanation: Since the first two intervals [1,4] and [2,5] overlap, we merged them into
one [1,5].
Example 2:
Intervals: [[6,7], [2,4], [5,9]]
Output: [[2,4], [5,9]]
Explanation: Since the intervals [6,7] and [5,9] overlap, we merged them into one [5,9].
Example 3:
Intervals: [[1,4], [2,6], [3,5]]
Output: [[1,6]]
https://www.geeksforgeeks.org/find-the-number-of-islands-using-dfs/
https://www.designgurus.io/course-play/grokking-the-coding-interview
> Exercise 5 Cyclic Sort
We are given an array containing n distinct numbers taken from the range 0 to n.
Since the array has only n numbers out of the total n+1 numbers, find the missing number.
Example 1:
Input: [4, 0, 3, 1]
Output: 2
Example 2:
Input: [8, 3, 5, 2, 4, 6, 0, 1]
Output: 7