Freaks City

Overview of Backtracking Backtracking is a systematic way to explore all potential solutions by building combinations incrementally and backtracking when a path fails to meet constraints. It's particularly useful for problems like combinations, permutations, subsets, and other combinatorial searches. Common problem types solved with backtrackin ...

Merge two ascending sorted linked lists into a new sorted linked list. The new list is constructed by splicing together all nodes from the two input linked lists. Example 1: Input: l1 = [1,2,4], l2 = [1,3,4] Output: [1,1,2,3,4,4] Example 2: Input: l1 = [], l2 = [0] Output: [0] class Solution: def mergeTwoLists(self, list1: ListNode, list ...

LeetCode 92. Reverse Linked List II Problem Statement Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes from position left to position right and return the modified list. Solution Strategy A stack provides an elegant mechanism to reverse elements in-place without complex pointer man ...

Problem Description: There are n teams numbered from 0 to n - 1 in a tournament. You are given a 0-indexed 2D boolean matrix grid of size n * n. For all i, j such that 0 <= i, j <= n - 1 and i != j, if grid[i][j] == 1, then team i is stronger than team j; otherwise, team j is stronger than team i. If there is no team that is stronger than ...

Implementing strStr() with the KMP Algorithm Given a haystack string and a needle string, locate the index of the first occurrence of the needle. The Knuth–Morris–Pratt (KMP) algorithm avoids redundant comparisons by precomputing a prefix table (often called the LPS – Longest Proper Prefix which is also Suffix – array). First, construct the LPS ...

Problem Description Given a string s and an integer array spaces, you need to insert a space before the character at each index specified in the spaces array. The spaces array is sorted in strictly increasing order, and all indices are valid (within the bounds of the string). Return the modified string after inserting the spaces. Examples Examp ...

1907. Categorize Salary Counts Table: Accounts +-------------+------+ | Column | Type | +-------------+------+ | account_id | int | | income | int | +-------------+------+ account_id is the primary key. Each row has monthly income of a bank account. Query the number of accounts in each salary category: Low Salary: income < 200 ...

Problem Description Given a non-strictly increasing (sorted with possible duplicates) integer aray nums, remove the duplicates in-place succh that each unique element appears only once. Maintain the relative order of the unique elements and return the number of unique elements in nums. Let k be the count of unique elements. To pass the test cas ...

Problem Understanding The challenge requires removing specific values from an array while meeting these constraints: Use only O(1) additional space and modify the input array in-place Element ordering can be changed Focus only on elements within the new length boundary The solution will be validated using code similar to: int result_length = ...

The three-sum problem requires finding all unique triplets in an array that add up to zero. While depth-first search can solve this after sorting, a more efficient approach uses the two-pointer technique on a sorted array. Key Points Use two pointers, not a single pointer—common mistake to avoid Recommended solving time: 20 minutes Problem De ...