Dictionary in Python is hash map & complexity is amortized to O(1)

Construct Binary Tree from Preorder and Inorder Traversal

Preorder: [3, 9, 20, 15, 7], Inorder: [9, 3, 15, 20, 7] First in the preorder traversal is 3 which is root Locate the…

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Permutations of distinct numbers - Not a brute force, but recursion

Permutations of given distinct elements

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Next Greater Element using Stack

Find next greater element for each element in given array. Check problem statement at https://www.

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Stack vs recursion. Recursion is better. Push element to bottom of stack. Reverse the stack.

Anything which is possible to solve using stack; it also can be solved using recursion. Since, system itself builds…

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Unique pairs count with positive difference. Two Pointers. Solved!

Given an array of integers, and a non-negative integer , count all distinct pairs with difference equal to , i.e.

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Pair with a Difference existence. Two Pointers. Solved!

Given an array of integers, and an integer , Determine whether or not there exist two elements in whose difference is…

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Count pairs with given Sum in an array

Given an array of integers, and an integer , find the number of pairs of elements in the array whose sum is equal to .

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Check whether Pair with a Sum exists. Solved!

Given an array of integers, and an integer , Determine whether or not there exist two elements in whose sum is exactly .

Merge Sort Algorithm - Recursion

Print the sorted array using merge sort algorithm

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Efficiently combine two sorted arrays

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