ServiceNow Interview Guide

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#1. Longest Substring Without Repeating Characters

StringsTwo PointersSliding Windows

Find the length of the longest substring within a given string that contains no repeating characters. The substring must be contiguous.

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Subarrays with K Different Integers

Given an array of integers, find the number of subarrays that contain exactly K distinct integers. A subarray is a contiguous part of the array.

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#2. Subarrays with K Different Integers

Given an array of integers, find the number of subarrays that contain exactly K distinct integers. A subarray is a contiguous part of the array.

This question is very likely to be asked in your ServiceNow interview

Trapping Rain Water

Given an array representing the height of bars, calculate how much water can be trapped between them after rain. Think about finding the maximum height to the left and right of each bar.

ArraysTwo PointersDynamic ProgrammingStacks

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#3. Trapping Rain Water

ArraysTwo PointersDynamic ProgrammingStacks

Given an array representing the height of bars, calculate how much water can be trapped between them after rain. Think about finding the maximum height to the left and right of each bar.

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Subarray Product Less Than K

Find the number of contiguous subarrays within a given array whose product is strictly less than a target value k. The goal is to efficiently count these subarrays by considering the product of their elements.

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#4. Subarray Product Less Than K

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Valid Parentheses

Determine if a string containing parentheses is valid. A valid string has matching and properly nested opening and closing parentheses.

StringsStacks

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#5. Valid Parentheses

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Determine if a string containing parentheses is valid. A valid string has matching and properly nested opening and closing parentheses.

StringsStacks

Group Anagrams

Given a list of words, group together all the anagrams. Anagrams are words that contain the same letters rearranged.

ArraysStrings

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#6. Group Anagrams

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Given a list of words, group together all the anagrams. Anagrams are words that contain the same letters rearranged.

ArraysStrings

LRU Cache

Design a data structure that acts as a Least Recently Used (LRU) cache. Implement methods to get and put key-value pairs, evicting the least recently used entry when the cache is full.

Linked ListsArraysDesign

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#7. LRU Cache

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Design a data structure that acts as a Least Recently Used (LRU) cache. Implement methods to get and put key-value pairs, evicting the least recently used entry when the cache is full.

Linked ListsArraysDesign

Number of Distinct Roll Sequences

Find the number of distinct sequences you can generate by rolling a die 'n' times, subject to certain constraints on consecutive rolls. Specifically, you cannot roll the same number twice in a row, and specific pairs of rolls are forbidden.

Dynamic Programming

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#8. Number of Distinct Roll Sequences

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Dynamic Programming

Generate Parentheses

Given a number 'n', generate all possible well-formed (balanced) parentheses strings of length 2*n. For instance, if n=3, you need to create all valid combinations like '((()))', '(()())', etc.

StringsRecursionBacktracking

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#9. Generate Parentheses

StringsRecursionBacktracking

Given a number 'n', generate all possible well-formed (balanced) parentheses strings of length 2*n. For instance, if n=3, you need to create all valid combinations like '((()))', '(()())', etc.

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Lexicographically Smallest String After Operations With Constraint

You're given a string and allowed to swap adjacent characters under certain constraints. Find the lexicographically smallest string you can achieve after performing these swaps.

Greedy AlgorithmsArrays

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#10. Lexicographically Smallest String After Operations With Constraint

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You're given a string and allowed to swap adjacent characters under certain constraints. Find the lexicographically smallest string you can achieve after performing these swaps.

Greedy AlgorithmsArrays

Find Minimum Diameter After Merging Two Trees

You're given two separate tree structures. Find the smallest possible diameter of the tree formed after merging the two trees at any possible nodes.

GraphsTrees

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#11. Find Minimum Diameter After Merging Two Trees

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You're given two separate tree structures. Find the smallest possible diameter of the tree formed after merging the two trees at any possible nodes.

GraphsTrees

Container With Most Water

You are given an array representing the heights of vertical lines. Find two lines that, together with the x-axis, form a container that holds the most water.

ArraysTwo PointersGreedy Algorithms

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#12. Container With Most Water

ArraysTwo PointersGreedy Algorithms

You are given an array representing the heights of vertical lines. Find two lines that, together with the x-axis, form a container that holds the most water.

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Best Time to Buy and Sell Stock

You're given daily stock prices. Find the maximum profit you can make by buying and selling the stock once. You must buy before you sell.

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#13. Best Time to Buy and Sell Stock

You're given daily stock prices. Find the maximum profit you can make by buying and selling the stock once. You must buy before you sell.

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Merge Intervals

You are given a collection of intervals. Merge all overlapping intervals into a single interval and return the result.

ArraysSorting

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#14. Merge Intervals

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You are given a collection of intervals. Merge all overlapping intervals into a single interval and return the result.

ArraysSorting

Move Zeroes

Given an array, rearrange it so that all zeros are moved to the end while maintaining the relative order of the non-zero elements.

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#15. Move Zeroes

Given an array, rearrange it so that all zeros are moved to the end while maintaining the relative order of the non-zero elements.

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Design HashMap

Implement a basic hash map data structure. You'll need to handle storing key-value pairs, retrieving values by key, and removing entries.

ArraysLinked Lists

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#16. Design HashMap

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Implement a basic hash map data structure. You'll need to handle storing key-value pairs, retrieving values by key, and removing entries.

ArraysLinked Lists

Zigzag Conversion

Convert a given string into a zigzag pattern with a specified number of rows. Then read the characters row by row to return the converted string.

Strings

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#17. Zigzag Conversion

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Convert a given string into a zigzag pattern with a specified number of rows. Then read the characters row by row to return the converted string.

Strings

First Missing Positive

Find the smallest positive integer that is missing from a given array of integers. You need to do this in linear time and constant extra space.

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#18. First Missing Positive

Find the smallest positive integer that is missing from a given array of integers. You need to do this in linear time and constant extra space.

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Number of Islands

Given a grid representing land and water, count the number of distinct islands. An island is formed by connected land cells.

ArraysGraphs

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#19. Number of Islands

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Given a grid representing land and water, count the number of distinct islands. An island is formed by connected land cells.

ArraysGraphs

Two Sum

Find two numbers in a given array that add up to a specific target value, and return their indices. Essentially, you need to efficiently locate the pair that satisfies the sum requirement.

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#20. Two Sum

Find two numbers in a given array that add up to a specific target value, and return their indices. Essentially, you need to efficiently locate the pair that satisfies the sum requirement.