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01 Two Sum Easy

Given an array of integers nums and an integer target, return indices of the two numbers that add up to target. Exactly one solution exists, may not use the same element twice.

Example 1

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

Example 2

Input:  nums=[3,2,4], target=6
Output: [1,2]

Test Cases

TC 1[2,7,11,15], 9 → [0,1]

TC 2[3,2,4], 6 → [1,2]

TC 3[3,3], 6 → [0,1]

TC 4[1,5,3,2], 4 → [2,3]

Constraints

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

02 Longest Substring Without Repeating Med

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

Example

Input:  s = "abcabcbb"
Output: 3  // "abc"

Test Cases

TC 1"abcabcbb" → 3

TC 2"bbbbb" → 1

TC 3"pwwkew" → 3

Constraints

0 ≤ s.length ≤ 5×10⁴
English letters, digits, symbols

03 Merge K Sorted Lists Hard

Given an array of k linked-lists, each sorted ascending, merge all into one sorted linked-list. Use a min-heap for O(N log k) efficiency.

Test Cases

TC 1[[1,4,5],[1,3,4],[2,6]] → [1,1,2,3,4,4,5,6]

TC 2[] → []

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🎥 Video

Alex (IR)

Riya (CA)

💬 Chat

Session started · both participants connected

Alex09:12

Hi Riya! Let's start with Two Sum. Think aloud as you go 🙂

Riya09:13

Thanks! I'll use a hashmap — O(n) time, O(n) space.

Alex09:14

Perfect, go for it!

Riya09:16

Done! Should I add empty array edge case handling?