Cisco Coding Interview Questions

Longest Palindromic Substring

Given a string s, return the longest palindromic substring in s.

House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from rob...

Predict the Winner

You are given an integer array nums. Two players are playing a game with this array: player 1 and player 2.

Lucky Numbers in a Matrix

Given an m x n matrix of distinct numbers, return all lucky numbers in the matrix in any order.

Rotate Image

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

Spiral Matrix

Given an m x n matrix, return all elements of the matrix in spiral order.

Fizz Buzz

Given an integer n, return a string array answer (1-indexed) where:

Snakes and Ladders

You are given an n x n integer matrix board where the cells are labeled from 1 to n2 in a Boustrophedon style starting from the bottom left of the board (i.e. b...

LRU Cache

Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.

Number of Valid Words in a Sentence

A sentence consists of lowercase letters ('a' to 'z'), digits ('0' to '9'), hyphens ('-'), punctuation marks ('!', '.', and ','), and spaces (' ') only. Each se...

Merge Intervals

Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cove...

Maximum Difference Between Increasing Elements

Given a 0-indexed integer array nums of size n, find the maximum difference between nums[i] and nums[j] (i.e., nums[j] - nums[i]), such that 0 <= i < j < n and...

Find the Largest Area of Square Inside Two Rectangles

There exist n rectangles in a 2D plane with edges parallel to the x and y axis. You are given two 2D integer arrays bottomLeft and topRight where bottomLeft[i]...

Minimum Cost to Make Array Equal

You are given two 0-indexed arrays nums and cost consisting each of n positive integers.

Maximum Subarray

Given an integer array nums, find the subarray with the largest sum, and return its sum.

Check if Binary String Has at Most One Segment of Ones

Given a binary string s ​​​​​without leading zeros, return true​​​ if s contains at most one contiguous segment of ones. Otherwise, return false.

Word Search II

Given an m x n board of characters and a list of strings words, return all words on the board.

Sum of k-Mirror Numbers

A k-mirror number is a positive integer without leading zeros that reads the same both forward and backward in base-10 as well as in base-k.

Implement Router

Design a data structure that can efficiently manage data packets in a network router. Each data packet consists of the following attributes:

Happy Number

Write an algorithm to determine if a number n is happy.

Max Points on a Line

Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane, return the maximum number of points that lie on the same straight line.

Two Sum

Given an array of integers nums and an integer target, return the indices of the two numbers that add up to target.

Stone Game

Alice and Bob play a game with piles of stones. There are an even number of piles arranged in a row, and each pile has a positive integer number of stones piles...

Trapping Rain Water

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.

Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

Cherry Pickup

You are given an n x n grid representing a field of cherries, each cell is one of three possible integers.

Longest Substring Without Repeating Characters

Given a string s, find the length of the longest substring without duplicate characters.

Merge Sorted Array

You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and num...

Decode String

Given an encoded string, return its decoded string.

Remove Boxes

You are given several boxes with different colors represented by different positive numbers.

Linked List Cycle

Given head, the head of a linked list, determine if the linked list has a cycle in it.

Best Time to Buy and Sell Stock

You are given an array prices where prices[i] is the price of a given stock on the ith day.

3Sum

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Number of Islands

Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.

Search a 2D Matrix

You are given an m x n integer matrix matrix with the following two properties:

Letter Combinations of a Phone Number

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.

Strange Printer

There is a strange printer with the following two special properties:

Move Zeroes

Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Reverse Linked List

Given the head of a singly linked list, reverse the list, and return the reversed list.

Longest Consecutive Sequence

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.

Validate IP Address

Given a string queryIP, return "IPv4" if IP is a valid IPv4 address, "IPv6" if IP is a valid IPv6 address or "Neither" if IP is not a correct IP of any type.

Add Two Numbers

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 sing...

Remove Duplicates from Sorted Array

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order o...

Valid Palindrome

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forwa...

Group Anagrams

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

Merge k Sorted Lists

You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.

Word Search

Given an m x n grid of characters board and a string word, return true if word exists in the grid.

Insert Delete GetRandom O(1)

Implement the RandomizedSet class:

Permutation in String

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise.

Single Number

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

Top K Frequent Elements

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

Gas Station

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

Find Servers That Handled Most Number of Requests

You have k servers numbered from 0 to k-1 that are being used to handle multiple requests simultaneously. Each server has infinite computational capacity but ca...

Expressive Words

Sometimes people repeat letters to represent extra feeling. For example:

Sliding Window Maximum

You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see...

Restore IP Addresses

A valid IP address consists of exactly four integers separated by single dots. Each integer is between 0 and 255 (inclusive) and cannot have leading zeros.

Beautiful Arrangement

Suppose you have n integers labeled 1 through n. A permutation of those n integers perm (1-indexed) is considered a beautiful arrangement if for every i (1 <= i...

Remove K Digits

Given string num representing a non-negative integer num, and an integer k, return the smallest possible integer after removing k digits from num.

Unique Paths II

You are given an m x n integer array grid. There is a robot initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-r...

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...

Largest Rectangle in Histogram

Given an array of integers heights representing the histogram's bar height where the width of each bar is 1, return the area of the largest rectangle in the his...

Find Minimum in Rotated Sorted Array

Suppose an array of length n sorted in ascending order is rotated between 1 and n times. For example, the array nums = [0,1,2,4,5,6,7] might become:

Permutations

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Jump Game

You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length...

Palindromic Substrings

Given a string s, return the number of palindromic substrings in it.

Unique Paths

There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner...

Edit Distance

Given two strings word1 and word2, return the minimum number of operations required to convert word1 to word2.

Pascal's Triangle

Given an integer numRows, return the first numRows of Pascal's triangle.

Product of Array Except Self

Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i].

Reverse Words in a String

Given an input string s, reverse the order of the words.

Missing Number

Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.

Subarray Sum Equals K

Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k.

Climbing Stairs

You are climbing a staircase. It takes n steps to reach the top.

Number of 1 Bits

Given a positive integer n, write a function that returns the number of set bits in its binary representation (also known as the Hamming weight).

Two Sum IV - Input is a BST

Given the root of a binary search tree and an integer k, return true if there exist two elements in the BST such that their sum is equal to k, or false otherwis...

Rising Temperature

Table: Weather

Longest Palindromic Subsequence

Given a string s, find the longest palindromic subsequence's length in s.

Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

Count of Integers

You are given two numeric strings num1 and num2 and two integers maxsum and minsum. We denote an integer x to be good if:

Design Browser History

You have a browser of one tab where you start on the homepage and you can visit another url, get back in the history number of steps or move forward in the hist...

Kth Smallest Element in a BST

Given the root of a binary search tree, and an integer k, return the kth smallest value (1-indexed) of all the values of the nodes in the tree.

Can Place Flowers

You have a long flowerbed in which some of the plots are planted, and some are not. However, flowers cannot be planted in adjacent plots.

Maximum Product of Two Elements in an Array

Given the array of integers nums, you will choose two different indices i and j of that array. Return the maximum value of (nums[i]-1)(nums[j]-1).

Compare Version Numbers

Given two version strings, version1 and version2, compare them. A version string consists of revisions separated by dots '.'. The value of the revision is its i...