Complete Guidance on Data Structures

, DSA Problem-Solving Masterclass

50+ Interview Problems with Solutions



CONTENTS

PART 1: ARRAYS (15 Problems)

PART 2: STRINGS (10 Problems)

PART 3: LINKED LISTS (10 Problems)

PART 4: STACKS & QUEUES (8 Problems)

PART 5: TREES (7 Problems)




PART 1: ARRAYS - 15 PROBLEMS

PROBLEM 1: Two Sum

Difficulty: Easy
Asked By: Amazon, Google, Facebook
Question:
Given array of integers and target, return indices of two numbers that add up to target.
Example:

Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: nums[0] + nums[1] = 2 + 7 = 9


Solution 1: Brute Force O(n2)

def twoSum(nums, target):
for i in range(len(nums)):
for j in range(i + 1, len(nums)):
if nums[i] + nums[j] == target:
return [i, j]


Solution 2: Hash Map (Optimal) O(n)




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