Problem Summary

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list.

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Problem Summary

Sort a linked list in O(NlogN) time using constant space complexity.

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Problem Summary

There are N gas stations along a circular route, where the amount of gas at station i is gas[i].

You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of the gas stations.

Find the index of the starting gas station if you can travel around the circuit once, otherwise return -1.
The solution is guaranteed to be unique.

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Problem Summary

Given an array of N integers, calculate the number of swaps you need to perfom to sort the array in ascending order. You can only swap adjacent elements.

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Problem Summary

Given N integers in order, for each ith integer, add it to a running list of integers, find the median of the updated list and print the median. (1 ≤ N ≤ 10^5)

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Problem Summary

Given string A representative a positive integer which has N digits, remove any k digits of the number, the remaining digits are arranged according to the original order to become a new positive integer.

Find the smallest integer after remove k digits. k ≤ N ≤ 240.

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Problem Summary

Given four integer arrays A,B,C,D, which have the same length of N where 0 ≤ N ≤ 500, compute the number of tuples (i,j,k,l) such that A[i] + B[j] + C[k] + D[l] == 0.

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Problem Summary

1. Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.

2. What if the tree is just a binary tree ?

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Problem Summary

Given N strings. Each string contains only lowercase letters from a to j(both inclusive). The set of N strings is said to be “GOOD SET” if no string is prefix of another string. Else, it is “BAD SET”.
(If two strings are identical, they are considered prefixes of each other.)

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Problem Summary

Search for the value T in an M x N matrix and return the occurrence of it.

This matrix has the following properties:

1. Integers in each row are sorted from left to right.
2. Integers in each column are sorted from up to bottom.
3. No duplicate integers in each row or column.

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