🚀 Coding Interview Questions with Answers (Part 20)

1️⃣9️⃣1️⃣ What is the Two Sum Problem?

Answer:

The Two Sum problem asks you to find two elements in an array whose sum equals a given target.

Example:

Input: [2][7][11][15]

Target: 9

Output: [2][7]

A Hash Map can be used to store previously seen values and find the required complement efficiently.

Time Complexity: O(n)

Space Complexity: O(n)

1️⃣9️⃣2️⃣ What is the Longest Substring Without Repeating Characters Problem?

Answer:

The goal is to find the longest substring that contains no repeated characters.

Example:

Input: "abcbb"

Output: 3

The longest substring is "abc".

A Sliding Window with a Hash Set or Hash Map can solve this efficiently.

Time Complexity: O(n)

Space Complexity: O(k)

1️⃣9️⃣3️⃣ What is the Longest Common Subsequence (LCS) Problem?

Answer:

LCS finds the longest sequence that appears in the same order in two strings, but the characters do not need to be adjacent.

Example:

Input: "abcde" and "ace"

Output: "ace"

Dynamic Programming is commonly used to solve this problem.

Time Complexity: O(m × n)

Space Complexity: O(m × n)

1️⃣9️⃣4️⃣ What is the Longest Increasing Subsequence (LIS) Problem?

Answer:

LIS finds the longest subsequence of an array where the elements are in strictly increasing order.

Example:

Input: [10][9][2][5][3][7][101][18]

Output: 4

One possible LIS is: [2][3][7][101]

It can be solved using Dynamic Programming or an optimized Binary Search approach.

Time Complexity: O(n log n) using the optimized approach.

1️⃣9️⃣5️⃣ What is the Maximum Subarray Sum Problem?

Answer:

The goal is to find the contiguous subarray with the largest possible sum.

Example:

Input: [-2][1][-3][4][-1][2][1][-5][4]

Output: 6

The maximum-sum subarray is: [4][-1][2][1]

Kadane's Algorithm can solve this efficiently.

Time Complexity: O(n)

Space Complexity: O(1)

1️⃣9️⃣6️⃣ What is the Merge Intervals Problem?

Answer:

The Merge Intervals problem requires combining overlapping intervals into a single interval.

Example:

Input: [[1,3][2,6][8,10][9,12]]

Output: [[1,6][8,12]]

The typical approach is to sort the intervals by their starting value and then merge overlapping intervals.

Time Complexity: O(n log n)

Space Complexity: O(n)

1️⃣9️⃣7️⃣ What is the Trapping Rain Water Problem?

Answer:

The problem asks you to calculate how much rainwater can be trapped between bars of different heights.

Example:

Input: [0][1][0][2][1][0][1][3][2][1][2][1]

Output: 6

A Two Pointers approach can solve this problem efficiently by tracking the maximum height from both sides.

Time Complexity: O(n)

Space Complexity: O(1)

1️⃣9️⃣8️⃣ What is the Median of Two Sorted Arrays Problem?

Answer:

The goal is to find the median of two sorted arrays without necessarily merging them completely.

Example:

Input: [1][3] and [2]

Output: 2

An optimized solution uses Binary Search to partition the two arrays correctly.

Time Complexity: O(log(min(m,n)))

Space Complexity: O(1)

1️⃣9️⃣9️⃣ What is the LRU Cache Problem?

Answer:

LRU stands for Least Recently Used.