Leetcode Questions Solutions Explained

Explain the detect capital problem (leetcode 520) by verifying all uppercase, all lowercase, or only the first letter uppercase, using ascii ranges and per-character checks.

Use a two-pointer approach to place even numbers at even indices and odd numbers at odd indices in LeetCode 922, swapping misplaced elements until the array is correctly rearranged.

determine whether an integer is a palindrome without strings by reversing digits to half and comparing with the original; ignore negatives and trailing zeros, handle odd lengths with reverse/10.

Master the longest substring without repeating characters using a two-pointer and set approach, tracking the maximum unique-character window as you slide and adjust for duplicates.

Use Gauss formula to find the missing number in an array, achieving linear runtime and constant space by comparing the expected sum from zero to N with the actual sum.

Partition a linked list around a value x, preserving the original order, by building two lists for nodes less than and greater or equal to x, then merging them.

Solve the Leetcode 64 minimum path sum from the top-left to bottom-right in a non-negative grid by moving right or down, using a bottom-up dynamic programming approach.

Solve the first unique character in a string by building a 26-letter frequency array for lowercase letters, then return the first index with count one or -1 if none.

Identify all ten-letter DNA substrings that occur more than once by sliding a window across the sequence, tracking seen substrings with a set, and collecting duplicates for output.

Demonstrates how to detect and locate the start of a cycle in a linked list using slow and fast pointers, handling both cyclic and acyclic cases.

Learn a two-pointer solution with a dummy head to remove all duplicates from a sorted linked list, returning only distinct numbers in sorted order.

Merge k sorted lists into one sorted linked list using a min-heap priority queue, building the result with a dummy head and appending smallest nodes.

Learn to merge overlapping intervals by sorting start times and expanding ends to form a single consolidated list; use a lambda comparator and iterative merging to produce the result.

Explore removing all instances of a given value from an array in place, using in place modification with no extra memory, returning the new length while the order may change.