ZigZag Conversion 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) P A H N A P L S I I G Y I R And then read […]
Add Two Numbers You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. Input: (2 -> 4 -> 3) + (5 -> 6 […]
Longest Substring Without Repeating Characters Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for “abcabcbb” is “abc”, which the length is 3. For “bbbbb” the longest substring is “b”, with the length of 1. tags: hash table, […]
LRU Cache Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set. get(key) – Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1. set(key, value) – Set or […]
Median of Two Sorted Arrays There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). tag: divide and conquer, array, binary search 9/22/2015 update Rewrite it in c++ version. […]
Palindrome Number Determine whether an integer is a palindrome. Do this without extra space. Some hints: Could negative integers be palindromes? (ie, -1) If you are thinking of converting the integer to string, note the restriction of using extra space. You could also try reversing an integer. However, if you […]
Candy There are N children standing in a line. Each child is assigned a rating value. You are giving candies to these children subjected to the following requirements: Each child must have at least one candy. Children with a higher rating get more candies than their neighbors. What is the […]
Evaluate Reverse Polish Notation 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”, “/”, […]
Count and Say The count-and-say sequence is the sequence of integers beginning as follows: 1, 11, 21, 1211, 111221, … 1 is read off as “one 1” or 11. 11 is read off as “two 1s” or 21. 21 is read off as “one 2, then one 1” or 1211. […]
Letter Combinations of a Phone Number Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is given below. Input:Digit string “23” Output: [“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”]. Note: Although […]
