1. Problem Summary You are given an integer array nums.Your task is to find the smallest positive integer (greater than 0) that does not appear in the array. Important characteristics: Example interpretation:For input [3, 4, -1, 1], the smallest missing positive is 2. 2. Key Insights The answer is always in the range [1 ……

1. Problem Summary You are given two strings: Your task is to identify and return the extra character that appears in t but not in s. Important characteristics: Example interpretation:If s = “abcd” and t = “abcde”, the answer is ‘e’. 2. Key Insights Counting characters works but is unnecessary You could count occurrences of…

1. Problem Summary You are given two integer arrays: Stations form a circular route, meaning after the last station, you return to station 0. Your task is to: Important constraints: 2. Key Insights Total fuel vs total cost determines feasibility If the total gas available is less than the total cost required: If a starting…

1. Problem Summary You are given two integers low and high.Your task is to return all numbers within this range (inclusive) that have sequential digits, meaning: Examples of sequential digits: Example interpretation:If low = 100 and high = 300, valid results include: 2. Key Insights Sequential digit numbers are limited There are very few valid…

1. Problem Summary You are given a string s consisting of upper-case letters, lower-case letters, and spaces. Your task is to return the length of the last word in the string, where: Example interpretation:For input “Hello World”, the last word is “World” and the result is 5. 2. Key Insights Words are separated by spaces…

1. Problem Summary You are given an array nums where each element represents the amount of money stored in a house along a street. You must determine the maximum amount of money you can rob, with the restriction that: Example interpretation:If you rob house i, you cannot rob houses i-1 or i+1. 2. Key Insights…

1. Problem Summary You are given: Your task is to: Example interpretation:If the existing intervals are [[1,3], [6,9]] and the new interval is [2,5], after inserting and merging, the output becomes [[1,5], [6,9]]. 2. Key Insights The original intervals are already: This allows a linear scan. Three logical phases occur: Overlapping rule Two intervals overlap…

1. Problem Summary You are given two integers: Your task is to return all unique combinations of exactly k distinct numbers where: The result must contain only valid combinations, and the order of combinations does not matter. Example interpretation:If k = 3 and n = 7, one valid combination is [1, 2, 4] because: 2.…

1. Problem Summary You are given an integer array nums.Your task is to find the contiguous subarray (containing at least one number) that has the maximum product, and return that product. Important characteristics of this problem: Example interpretation:Given [-2, 3, -4], the maximum product subarray is [3, -4], whose product is -12, but the full…

1. Problem Summary You are given the root of a binary tree. Your task is to determine the maximum depth of the tree. The depth of a binary tree is defined as: A leaf node is one that has no left or right child. Example understanding:If the longest path contains nodes [1 → 3 →…