Author: Hashim

Today we will talk about “Longest Palindromic Substring” problem. I’ve developed solution about year ago but a few days remembered it and thought about it. So, full problem description: Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. Ok, good, on the face of it, we can use some simple naive algorithm with O^2 complexity…

I’ve just solved one more problem from leetcode and going to share that solution. So, solved problem calls Binary Tree Maximum Path Sum. Problem description: Given a binary tree, find the maximum path sum. The path may start and end at any node in the tree. For example: Given the below binary tree, 1 / \ 2 3 Return 6. OK, stop and think …. What do we have ???  The main point is binary tree. We can…

I’ve solved a few tasks from http://leetcode.com/ and going to publish my solutions, So, first task is Evaluate Reverse Polish Notation The task description is : Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, –, *, /. Each operand may be an integer or another expression. Some examples:   [“2”, “1”, “+”, “3”, “*”] -> ((2 + 1) * 3) -> 9   [“4”, “13”, “5”, “/”, “+”] -> (4 + (13 / 5)) ->…

I’ve just opened Introduction to Algorithms on Divide-and-Conquer chapter, and found interesting item – The maximum-subarray problem. In book you can find implementation with complexity O(NlogN) with good explanation, but in Exercises part there is good task: Use the following ideas to develop a nonrecursive, linear-time algorithm for the maximum-subarray problem. Start at the left end of the array, and progress toward the right, keeping track of the maximum subarray seen so far. Knowing a…

We are working on next task from leetcode. So, next task will be …. , {Single Number} 🙂. Task: Given an array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? Stop and think … What we have, input array of integers and we should find one NOT DUPLICATE number. So, it’s easy … Go to the…