CATEGORY: HARD Problem Design a stack-like data structure to push elements to the stack and pop the most frequent element from the stack. Implement the FreqStack class: FreqStack() constructs an empty frequency stack. void push(int val) pushes an integer val onto the top of the stack. int pop() removes and returns the most frequent element in the stack. If there is a …
CATEGORY: MEDIUM Problem The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
1 2 3 | P A H N A P L S I I G Y I R |
And then read line by line: “PAYPALISHIRING” Write the code that will take a string and make this conversion given a number …
Category: Medium Problem A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below). How many …
Category: Easy Problem Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters. Letters are case sensitive, for example, “Aa” is not considered a palindrome here. Problem Link. Examples Example 1: Example 2: Constraints 1 <= s.length <= 2000 s consists of lowercase and/or uppercase English letters only. Solution Approach In this …
Leetcode 409: Longest Palindrome | Leetcode Easy Read More »
Category: Easy Problem You are given an m x n integer grid accounts where accounts[i][j] is the amount of money the ith customer has in the jth bank. Return the wealth that the richest customer has. A customer’s wealth is the amount of money they have in all their bank accounts. The richest customer is the customer that has the maximum wealth. Problem Link. Examples Example 1: Example 2: Constraints …
Category: Easy Problem Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. Follow up: Could you implement a solution with a linear runtime complexity and without using extra memory? Problem Link. Examples Example 1: Example 2: Constraints 1 <= nums.length <= 3 * 104 -3 * 104 <= nums[i] <= 3 * 104 …
Category: Easy Problem Given an array nums and a value val, remove all instances of that value in-place and return the new length. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory. The order of elements can be changed. It doesn’t matter what you leave beyond the new length. https://leetcode.com/problems/remove-element Examples Example …
Category: Medium Problem Given the head of a linked list, remove the nth node from the end of the list and return its head. Follow up: Could you do this in one pass? https://leetcode.com/problems/remove-nth-node-from-end-of-list Examples Example 1: Example 2: Example 3: Solution Approach In this problem of “remove nth node from the list”, we are given a linked list whose …
Category: Easy Problem Given a non-empty array of decimal digits representing a non-negative integer, increment one to the integer. The digits are stored such that the most significant digit is at the head of the list, and each element in the array contains a single digit. You may assume the integer does not contain any leading zero, except the …
Category: Medium Problem You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list. You may assume the two numbers do not contain any leading zero, except the number 0 itself. …
