Freaks City

Problem 1: Find N Unique Integers Sum up to Zero Given an integer n, any array of n unique integers that sum to 0 can be returned. Example 1: Input: n = 5 Output: [-7,-1,1,3,4] Explanation: These arrays are also correct [-5,-1,1,2,3], [-3,-1,2,-2,4]. Example 2: Input: n = 3 Output: [-1,0,1] Example 3: Input: n = 1 Output: [0] Constraints: 1 &l ...

Finding the Bottom Left Tree ValueLocating the leftmost value in the last row of a binary tree can be efficiently achieved using Breadth-First Search (BFS). By processing the tree level by level, the first node encountered at each depth represents the leftmost node for that specific row. Upon completing the traversal, the value recorded for the ...

Magic Pocket Subset Sum The Magic Pocket problem requires determining the number of ways to select items such that their total volume equals exactly 40. This can be approached using a Depth-First Search (DFS) strategy where we explore every possible combination of including or excluding an item. We maintain a running sum of the selected volumes ...

This problem can be efficiently solved using a depth-first search (DFS) algorithm with backtracking. The core idea is to traverse each cell of the grid and check if it can start a valid path that forms the target word. Key Concepts The grid trvaersal here is a variation of binary tree DFS, where each cell (node) has four possible adjacent direc ...

Problem 1: Counting Valid Sets In this problem, the floor operation does not affect the correcntess, so a brute-force DFS approach is applicable. A critical observation: if the array contains the element \(1\), it must be skipped immediately. Otherwise, \(1\) could be selected infinitely many time, leading to incorrect results. Solution Code in ...

Insect Population Growth Problem Time Limit: C/C++ 1000ms, Other Languages 2000ms Memory Limit: C/C++ 256MB, Other Languages 512MB Problem Description Scientists in a tropical forest have discovered a special insect species with remarkable reproductive capabilities. Each pair of adult insects produces y pairs of eggs after x months. Each pair o ...

In-Order Traversal Recursive List<Integer> inorder(TreeNode node) { List<Integer> out = new ArrayList<>(); walk(node, out); return out; } void walk(TreeNode cur, List<Integer> acc) { if (cur == null) return; walk(cur.left, acc); acc.add(cur.val); walk(cur.right, acc); } Iterative (Single Sta ...

The Confounding Switches Time Limit: C/C++ 1000MS, Other Languages 2000MS Memory Limit: C/C++ 256MB, Other Languages 512MB Description Have you ever played the "Light Switch" game? There are \(25\) lights arranged in a \(5×5\) grid. Each light has a switch that can toggle its state. In each move, a player can toggle one light's sta ...

Suppose you are given an integer array arr. The goal is to split it into the fewest possible subsets such that every pair of elements inside the same subset is coprime (their greatest common divisor equals 1). We can solve this problem using a DFS backtracking approach. Below are two distinct strategies, each corresponding to a different way of ...

Recursion can be categorized into path-aware and path-unaware forms. Most tree-related recursions are path-aware. Fundamentally, recursion implements depth-first search (DFS). To solve problems recursively, treat the recursive function as a black box that handles a subproblem, then reuse it. Beginners often try to fully expand the recursion, wh ...