Interview Questions and Answers

The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones.

Example:

Fib(0) = 0, Fib(1) = 1, Fib(n) = Fib(n-1) + Fib(n-2)

Find the contiguous subarray with the largest sum.

Example:

Input: [-2, 1, -3, 4, -1, 2, 1, -5, 4], Output: 6 (subarray [4, -1, 2, 1])

A robot is located at the top-left corner of a m x n grid. It can only move either down or right. Find the number of unique paths to reach the bottom-right corner.

Example:

Input: m = 3, n = 7, Output: 28

Find the length of the longest subsequence of a given sequence such that all elements of the subsequence are sorted in increasing order.

Example:

Input: [10, 22, 9, 33, 21, 50, 41, 60, 80], Output: 6

Given a set of coin denominations, find the number of ways to make a certain amount of change.

Example:

Input: coins=[1, 2, 5], amount=5, Output: 4

Given weights and values of items, find the maximum value that can be obtained by selecting a subset of items with total weight not exceeding a given limit.

Example:

Weights: [2, 3, 4, 5], Values: [3, 4, 5, 6], Knapsack Capacity: 5, Output: 11

Given two sequences, find the length of the longest subsequence present in both of them.

Example:

Input: ABCBDAB, BDCAB, Output: 4 (BCAB)

Given a rod of length n and prices at which different lengths of the rod can be sold, find the maximum value obtainable by cutting up the rod.

Example:

Lengths: [1, 2, 3, 4, 5], Prices: [1, 5, 8, 9, 10], Rod Length: 4, Output: 10

Find the contiguous subarray within an array (containing at least one number) that has the largest product.

Example:

Input: [2, 3, -2, 4], Output: 6 (subarray [2, 3])

A message containing letters from A-Z can be encoded into numbers. Given a non-empty string containing only digits, determine the total number of ways to decode it.

Example:

Input: "226", Output: 3 ("22" can be decoded as "BB", "2" + "2" + "6" can be decoded as "VVF")

Given a non-empty string and a dictionary of words, determine if the string can be segmented into a space-separated sequence of one or more dictionary words.

Example:

Input: s = "leetcode", wordDict = ["leet", "code"], Output: true

Given a grid filled with non-negative numbers, find a path from the top-left to the bottom-right corner that minimizes the sum of numbers along the path.

Example:

Grid: [[1,3,1],[1,5,1],[4,2,1]], Output: 7 (1 -> 3 -> 1 -> 1 -> 1)

Given a string, find the longest substring which is a palindrome.

Example:

Input: "babad", Output: "bab" or "aba"

Given a non-empty array containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.

Example:

Input: [1, 5, 11, 5], Output: true (subset sums: [1, 5, 5] and [11])

Given two integer arrays, find the maximum length of a common subarray of both arrays.

Example:

Input: A = [1,2,3,2,1], B = [3,2,1,4,7], Output: 3 ([3, 2, 1])

Given a string, find the total number of palindromic substrings.

Example:

Input: "abc", Output: 3 ("a", "b", "c")

Given a 2D grid, find the minimum cost path from the top-left corner to the bottom-right corner.

Example:

Grid: [[1,3,1],[1,5,1],[4,2,1]], Output: 7 (1 -> 3 -> 1 -> 1 -> 1)

A sequence of numbers is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same. Return the total number of arithmetic slices in the array.

Example:

Input: [1, 2, 3, 4], Output: 3 (three arithmetic slices: [1, 2, 3], [2, 3, 4], [1, 2, 3, 4])

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.

Example:

Matrix: [[1, 0, 1, 0, 0], [1, 0, 1, 1, 1], [1, 1, 1, 1, 1], [1, 0, 0, 1, 0]], Output: 4

There are a row of n houses, each house can be painted with one of the three colors: red, blue, or green. The cost of painting each house with a certain color is different. You have to paint all the houses such that no two adjacent houses have the same color.

Example:

Costs: [[17, 2, 17], [16, 16, 5], [14, 3, 19]], Output: 10 (paint the first house blue, the second house green, and the third house blue)

You have d dice, and each die has f faces numbered 1 to f. Return the number of possible ways (out of f^d total ways) to roll the dice so the sum of the face-up numbers equals target.

Example:

d = 2, f = 6, target = 7, Output: 6 (possible rolls: [1,6], [2,5], [3,4], [4,3], [5,2], [6,1])

Given two strings, find the minimum number of operations required to convert one string into the other.

Example:

Input: word1 = "horse", word2 = "ros", Output: 3

Given a string, partition it into as many palindromic substrings as possible.

Example:

Input: aab, Output: [['a', 'a', 'b'], ['aa', 'b']]

Given a string, find the number of distinct palindromic subsequences of it.

Example:

Input: "bccb", Output: 6 ("b", "c", "c", "b", "ccb", "bccb")

Given an integer matrix, find the length of the longest increasing path.

Example:

Matrix: [[9,9,4],[6,6,8],[2,1,1]], Output: 4 (9 -> 6 -> 8 -> 1)

Implement regular expression matching with support for '.' and '*'.

Example:

Input: s = "aa", p = "a*", Output: true

Given an array representing stock prices, find the maximum profit that can be obtained with at most k transactions.

Example:

Input: [3, 2, 6, 5, 0, 3], k = 2, Output: 7

Given a string, find the number of distinct non-empty subsequences of the string.

Example:

Input: "abc", Output: 7 ("a", "b", "c", "ab", "ac", "bc", "abc")

Given a non-empty string and a dictionary of words, return all possible sentences formed by concatenating words from the dictionary.

Example:

Input: s = "catsanddog", wordDict = ["cat", "cats", "and", "sand", "dog"], Output: ["cats and dog", "cat sand dog"]

Given two words (beginWord and endWord), and a dictionary's word list, find all shortest transformation sequences from beginWord to endWord.

Example:

beginWord = "hit", endWord = "cog", wordList = ["hot","dot","dog","lot","log","cog"], Output: [["hit","hot","dot","dog","cog"],["hit","hot","lot","log","cog"]]