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Two Sum

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

Arrays Hash Table Easy Google
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85% Success

Valid Parentheses

Determine if the input string has valid parentheses combinations.

Stack String Easy Amazon
Not Started
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Merge Two Sorted Lists

Merge two sorted linked lists and return as a new sorted list.

Linked List Recursion Easy Microsoft
In Progress
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Maximum Subarray

Find the contiguous subarray with the largest sum.

Arrays Dynamic Programming Medium Facebook
Not Started
65% Success

Binary Tree Inorder

Return the inorder traversal of a binary tree's node values.

Tree DFS Medium Apple
Solved
73% Success

Longest Palindrome

Find the longest palindromic substring in a given string.

String Dynamic Programming Hard Netflix
Not Started
45% Success

Two Sum

Easy
Arrays Hash Table Google

Description

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

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Examples

Example 1:
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
Example 2:
Input: nums = [3,2,4], target = 6
Output: [1,2]

Constraints

  • • 2 ≤ nums.length ≤ 10⁴
  • • -10⁹ ≤ nums[i] ≤ 10⁹
  • • -10⁹ ≤ target ≤ 10⁹
  • • Only one valid answer exists

Hints

💡 Try using a hash map to store values and their indices
💡 For each element, check if target - element exists in the map
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class Solution:
def twoSum(self, nums: List[int], target: int) -> List[int]:
hashmap = {}
for i, num in enumerate(nums):
complement = target - num
if complement in hashmap:
return
hashmap[num] = i
return
Runtime: O(n) | Memory: O(n)

Test Results

3/3 passed
✓ Test Case 1 2ms
Input: [2,7,11,15], 9 → Output: [0,1]
✓ Test Case 2 1ms
Input: [3,2,4], 6 → Output: [1,2]
✓ Test Case 3 1ms
Input: [3,3], 6 → Output: [0,1]

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CodeMaster_Pro

• 2 hours ago

Just solved "Longest Palindromic Substring" in O(n) time! The Manacher's algorithm is mind-blowing 🤯

Longest Palindromic Substring
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ByteNinja

• 4 hours ago

Finally cracked the Google interview! Thanks to everyone who helped me prepare. The key was consistent practice on this platform 🚀

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John Doe

@johndoe • Software Engineer at Google

San Francisco, CA • Joined March 2023

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