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Different coding problem patterns implemented in Python. A brief overview of common data structures and algorithms.

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Popular Coding Problem Solving Patterns

Data Structures Overview

Array

Array

  • A list of similar values
  • Can be used to store anything
  • Stores values of the same data type
  • Every item in an array is called an element
  • 3 attributes:
    • Name
    • Type
    • Size
      • set integer that is fixed upon the creation of an array
      • CAN'T be changed once created
  • Parallel arrays
    • 2 or more arrays which
      • contain the same # of elements
      • have corresponding values in the same position
  • Creating an array
    • populate with elements
    • set a specific size
    • Python - array = [1, 2, 3]
  • To get information, we use a numerical index
    • An integer which corresponds to an element within the array
  • A two-dimensional array is an array with an array at each index
Stack

Stack

  • A data structure in which we add elements and remove elements according to the LIFO (last in first out) principle
    • only one way in and one way out for the data
  • Common Stack Methods
    • push - adds an object into the top of the stack (Push(Object))
    • pop - remove an element from the top of the stack (Pop())
    • peek - allows you to get the value at the top of the list without removing it
    • contains - searching throughout the stack (Contains(Object)) - w/o having to take elements off the stack
Queue

Queue

  • The sequential access data structure which follows the FIFO methodology (First In First Out)
  • Add to the back and remove from the front
  • Queue methods
    • Enqueue - Adds element to the tail of the queue
    • Dequeue - Removes element from the head of the queue
    • Peek - returns the object that's at the forefront of the queue without removing it
    • Contains - returns whether or not the queue contains an object (boolean)

Problem Solving Patterns

Sliding Window

S.No. Topic: Problem Solutions Python C++ Java
1 Sliding Window Minimum Size Subarray Sum ✔️
2 Sliding Window Find the maximum and minimum element in an array ✔️
3 Sliding Window Find the "Kth" max and min element of an array ✔️
4 Sliding Window Given an array which consists of only 0, 1 and 2. Sort the array without using any sorting algo ✔️
5 Sliding Window Move all the negative elements to one side of the array ✔️
6 Sliding Window Find the Union and Intersection of the two sorted arrays. ✔️
7 Sliding Window Write a program to cyclically rotate an array by one. ✔️
8 Sliding Window find Largest sum contiguous Subarray [V. IMP] ✔️
9 Sliding Window Minimise the maximum difference between heights [V.IMP] ✔️
10 Sliding Window Minimum no. of Jumps to reach end of an array ✔️


Two Pointers

S.No. Topic: Problem Solutions Python C++ Java
1 Matrix Spiral traversal on a Matrix ✔️
2 Matrix Search an element in a matriix ✔️
3 Matrix Find median in a row wise sorted matrix ✔️
4 Matrix Find row with maximum no. of 1's ✔️
5 Matrix Print elements in sorted order using row-column wise sorted matrix ✔️
6 Matrix Maximum size rectangle ✔️
7 Matrix Find a specific pair in matrix ✔️
8 Matrix Rotate matrix by 90 degrees ✔️
9 Matrix Kth smallest element in a row-cpumn wise sorted matrix ✔️
10 Matrix Common elements in all rows of a given matrix ✔️


Fast & Slow Pointers

S.No. Topic: Problem Solutions Python C++ Java
1 String Reverse a String ✔️
2 String Check whether a String is Palindrome or not ✔️
3 String Find Duplicate characters in a string ✔️
4 String Why strings are immutable in Java? ❌
5 String Write a Code to check whether one string is a rotation of another ✔️
6 String Write a Program to check whether a string is a valid shuffle of two strings or not ✔️
7 String Count and Say problem ❌
8 String Write a program to find the longest Palindrome in a string.[ Longest palindromic Substring] ❌
9 String Find Longest Recurring Subsequence in String ❌
10 String Print all Subsequences of a string. ❌


Merge Intervals

S.No. Topic: Problem Solutions Python C++ Java
1 Searching & Sorting Find first and last positions of an element in a sorted array ✔️
2 Searching & Sorting Find a Fixed Point (Value equal to index) in a given array ✔️
3 Searching & Sorting Search in a rotated sorted array ✔️
4 Searching & Sorting square root of an integer ✔️
5 Searching & Sorting Maximum and minimum of an array using minimum number of comparisons ✔️
6 Searching & Sorting Optimum location of point to minimize total distance ❌


Cyclic Sort

S.No. Topic: Problem Solutions Python C++ Java
1 LinkedList Write a Program to reverse the Linked List. (Both Iterative and recursive) ❌
2 LinkedList Reverse a Linked List in group of Given Size. [Very Imp] ❌
3 LinkedList Write a program to Detect loop in a linked list. ❌
4 LinkedList Write a program to Delete loop in a linked list. ❌
5 LinkedList Find the starting point of the loop. ❌


In-place Reversal of a LinkedList

S.No. Topic: Problem Solutions Python C++ Java
1 Binary Trees level order traversal ❌
2 Binary Trees Reverse Level Order traversal ❌
3 Binary Trees Height of a tree ❌
4 Binary Trees Diameter of a tree ❌
5 Binary Trees Mirror of a tree ❌
6 Binary Trees Inorder Traversal of a tree both using recursion and Iteration ❌


Tree Breadth First Search

S.No. Topic: Problem Solutions Python C++ Java
1 Binary Search Trees Fina a value in a BST ❌
2 Binary Search Trees Deletion of a node in a BST ❌
3 Binary Search Trees Find min and max value in a BST ❌
4 Binary Search Trees Find inorder successor and inorder predecessor in a BST ❌
5 Binary Search Trees Check if a tree is a BST or not ❌
6 Binary Search Trees Populate Inorder successor of all nodes ❌
7 Binary Search Trees Find LCA of 2 nodes in a BST ❌
8 Binary Search Trees Construct BST from preorder traversal ❌
9 Binary Search Trees Convert Binary tree into BST ❌
10 Binary Search Trees Convert a normal BST into a Balanced BST ❌
11 Binary Search Trees Merge two BST [ V.V.V>IMP ] ❌
12 Binary Search Trees Find Kth largest element in a BST ❌
13 Binary Search Trees Find Kth smallest element in a BST ❌
14 Binary Search Trees Count pairs from 2 BST whose sum is equal to given value "X" ❌
15 Binary Search Trees Find the median of BST in O(n) time and O(1) space ❌
16 Binary Search Trees Count BST ndoes that lie in a given range ❌
17 Binary Search Trees Replace every element with the least greater element on its right ❌


Tree Depth First Search

S.No. Topic: Problem Solutions Python C++ Java
1 Greedy Activity Selection Problem ❌
2 Greedy Job SequencingProblem ❌
3 Greedy Huffman Coding ❌
4 Greedy Water Connection Problem ❌
5 Greedy Fractional Knapsack Problem ❌
6 Greedy Greedy Algorithm to find Minimum number of Coins ❌
7 Greedy Maximum trains for which stoppage can be provided ❌
8 Greedy Minimum Platforms Problem ❌
9 Greedy Buy Maximum Stocks if i stocks can be bought on i-th day ❌
10 Greedy Find the minimum and maximum amount to buy all N candies ❌
11 Greedy Minimize Cash Flow among a given set of friends who have borrowed money from each other ❌
12 Greedy Minimum Cost to cut a board into squares ❌
13 Greedy Check if it is possible to survive on Island ❌
14 Greedy Find maximum meetings in one room ❌
15 Greedy Maximum product subset of an array ❌
16 Greedy Maximize array sum after K negations ❌
17 Greedy Maximize the sum of arr[i]*i ❌
18 Greedy Maximum sum of absolute difference of an array ❌
19 Greedy Maximize sum of consecutive differences in a circular array ❌
20 Greedy Minimum sum of absolute difference of pairs of two arrays ❌
21 Greedy Program for Shortest Job First (or SJF) CPU Scheduling ❌
22 Greedy Program for Least Recently Used (LRU) Page Replacement algorithm ❌
23 Greedy Smallest subset with sum greater than all other elements ❌
24 Greedy Chocolate Distribution Problem ❌
25 Greedy DEFKIN -Defense of a Kingdom ❌
26 Greedy DIEHARD -DIE HARD ❌
27 Greedy GERGOVIA -Wine trading in Gergovia ❌
28 Greedy Picking Up Chicks ❌
29 Greedy CHOCOLA –Chocolate ❌
30 Greedy ARRANGE -Arranging Amplifiers ❌


Two Heaps

S.No. Topic: Problem Solutions Python C++ Java
1 BackTracking Rat in a maze Problem ❌
2 BackTracking Printing all solutions in N-Queen Problem ❌
3 BackTracking Word Break Problem using Backtracking ❌


Subsets

S.No. Topic: Problem Solutions Python C++ Java
1 Stacks & Queues Implement Stack from Scratch ❌
2 Stacks & Queues Implement Queue from Scratch ❌
3 Stacks & Queues Implement 2 stack in an array ❌
4 Stacks & Queues find the middle element of a stack ❌
5 Stacks & Queues Implement "N" stacks in an Array ❌
6 Stacks & Queues Check the expression has valid or Balanced parenthesis or not. ❌


Modified Binary Search

S.No. Topic: Problem Solutions Python C++ Java
1 Heap Implement a Maxheap/MinHeap using arrays and recursion. ❌
2 Heap Sort an Array using heap. (HeapSort) ❌
3 Heap Maximum of all subarrays of size k. ❌
4 Heap “k” largest element in an array ❌
5 Heap Kth smallest and largest element in an unsorted array ❌
6 Heap Merge “K” sorted arrays. [ IMP ] ❌
7 Heap Merge 2 Binary Max Heaps ❌


Bitwise XOR

S.No. Topic: Problem Solutions Python C++ Java
1 Graph Create a Graph, print it ❌
2 Graph Implement BFS algorithm ❌
3 Graph Implement DFS Algo ❌


Top K Elements

S.No. Topic: Problem Solutions Python C++ Java
1 Trie Construct a trie from scratch ❌
2 Trie Find shortest unique prefix for every word in a given list ❌
3 Trie Word Break Problem | (Trie solution) ❌
4 Trie Given a sequence of words, print all anagrams together ❌
5 Trie Implement a Phone Directory ❌
6 Trie Print unique rows in a given boolean matrix ❌


K-Way Merge

S.No. Topic: Problem Solutions Python C++ Java
1 Dynamic Programming Coin ChangeProblem ❌
2 Dynamic Programming Knapsack Problem ❌
3 Dynamic Programming Binomial CoefficientProblem ❌
4 Dynamic Programming Permutation CoefficientProblem ❌
5 Dynamic Programming Program for nth Catalan Number ❌
6 Dynamic Programming Matrix Chain Multiplication ❌
7 Dynamic Programming Edit Distance ❌
8 Dynamic Programming Subset Sum Problem ❌
9 Dynamic Programming Friends Pairing Problem ❌
10 Dynamic Programming Gold Mine Problem ❌
11 Dynamic Programming Assembly Line SchedulingProblem ❌
12 Dynamic Programming Painting the Fenceproblem ❌
13 Dynamic Programming Maximize The Cut Segments ❌
14 Dynamic Programming Longest Common Subsequence ❌
15 Dynamic Programming Longest Repeated Subsequence ❌
16 Dynamic Programming Longest Increasing Subsequence ❌
17 Dynamic Programming Space Optimized Solution of LCS ❌
18 Dynamic Programming LCS (Longest Common Subsequence) of three strings ❌
19 Dynamic Programming Maximum Sum Increasing Subsequence ❌
20 Dynamic Programming Count all subsequences having product less than K ❌
21 Dynamic Programming Longest subsequence such that difference between adjacent is one ❌
22 Dynamic Programming Maximum subsequence sum such that no three are consecutive ❌
23 Dynamic Programming Egg Dropping Problem ❌
24 Dynamic Programming Maximum Length Chain of Pairs ❌
25 Dynamic Programming Maximum size square sub-matrix with all 1s ❌
26 Dynamic Programming Maximum sum of pairs with specific difference ❌
27 Dynamic Programming Min Cost PathProblem ❌
28 Dynamic Programming Maximum difference of zeros and ones in binary string ❌
29 Dynamic Programming Minimum number of jumps to reach end ❌
30 Dynamic Programming Minimum cost to fill given weight in a bag ❌
31 Dynamic Programming Minimum removals from array to make max –min <= K ❌
32 Dynamic Programming Longest Common Substring ❌
33 Dynamic Programming Count number of ways to reacha given score in a game ❌
34 Dynamic Programming Count Balanced Binary Trees of Height h ❌
35 Dynamic Programming LargestSum Contiguous Subarray [V>V>V>V IMP ] ❌
36 Dynamic Programming Smallest sum contiguous subarray ❌
37 Dynamic Programming Unbounded Knapsack (Repetition of items allowed) ❌
38 Dynamic Programming Word Break Problem ❌
39 Dynamic Programming Largest Independent Set Problem ❌
40 Dynamic Programming Partition problem ❌
41 Dynamic Programming Longest Palindromic Subsequence ❌
42 Dynamic Programming Count All Palindromic Subsequence in a given String ❌
43 Dynamic Programming Longest Palindromic Substring ❌
44 Dynamic Programming Longest alternating subsequence ❌
45 Dynamic Programming Weighted Job Scheduling ❌
46 Dynamic Programming Coin game winner where every player has three choices ❌
47 Dynamic Programming Count Derangements (Permutation such that no element appears in its original position) [ IMPORTANT ] ❌
48 Dynamic Programming Maximum profit by buying and selling a share at most twice [ IMP ] ❌
49 Dynamic Programming Optimal Strategy for a Game ❌
50 Dynamic Programming Optimal Binary Search Tree ❌
51 Dynamic Programming Palindrome PartitioningProblem ❌
52 Dynamic Programming Word Wrap Problem ❌
53 Dynamic Programming Mobile Numeric Keypad Problem [ IMP ] ❌
54 Dynamic Programming Boolean Parenthesization Problem ❌
55 Dynamic Programming Largest rectangular sub-matrix whose sum is 0 ❌
56 Dynamic Programming Largest area rectangular sub-matrix with equal number of 1’s and 0’s [ IMP ] ❌
57 Dynamic Programming Maximum sum rectangle in a 2D matrix ❌
58 Dynamic Programming Maximum profit by buying and selling a share at most k times ❌
59 Dynamic Programming Find if a string is interleaved of two other strings ❌
60 Dynamic Programming Maximum Length of Pair Chain ❌


Bit Manipulation

S.No. Topic: Problem Solutions Python C++ Java
1 Bit Manipulation Count set bits in an integer ✔️
2 Bit Manipulation Find the two non-repeating elements in an array of repeating elements ✔️
3 Bit Manipulation Count number of bits to be flipped to convert A to B ✔️
4 Bit Manipulation Count total set bits in all numbers from 1 to n ✔️

5 Bit Manipulation Program to find whether a no is power of two ✔️
6 Bit Manipulation Find position of the only set bit ✔️
7 Bit Manipulation Copy set bits in a range ✔️
8 Bit Manipulation Divide two integers without using multiplication, division and mod operator ✔️
9 Bit Manipulation Calculate square of a number without using *, / and pow() ✔️
10 Bit Manipulation Power Set ✔️


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Different coding problem patterns implemented in Python. A brief overview of common data structures and algorithms.

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