How to Solve Collect Coins in a Tree Problem
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Collect Coins in a Tree
There exists an undirected and unrooted tree with n nodes indexed from 0 to n - 1. You are given an integer n and a 2D integer array edges of length n - 1, where edges[i] = [ai, bi] indicates that the...
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Understanding the Collect Coins in a Tree Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
There exists an undirected and unrooted tree with n nodes indexed from 0 to n - 1. You are given an integer n and a 2D integer array edges of length n - 1, where edges[i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the tree. You are also given an array coins of size n where coins[i] can be either 0 or 1, where 1 indicates the presence of a coin in the vertex i. Initially, you choose to start at any vertex in the tree. Then, you can perform the following operations any number of times: Collect all the coins that are at a distance of at most 2 from the current vertex, or Move to any adjacent vertex in the tree. Find the minimum number of edges you need to go through to collect all the coins and go back to the initial vertex. Note that if you pass an edge several times, you need to count it into the answer several times.
Collect Coins in a Tree
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Examples
coins = [1,0,0,0,0,1], edges = [[0,1],[1,2],[2,3],[3,4],[4,5]]2Start at vertex 2, collect the coin at vertex 0, move to vertex 3, collect the coin at vertex 5 then move back to vertex 2.
coins = [0,0,0,1,1,0,0,1], edges = [[0,1],[0,2],[1,3],[1,4],[2,5],[5,6],[5,7]]2Start at vertex 0, collect the coins at vertices 4 and 3, move to vertex 2, collect the coin at vertex 7, then move back to vertex 0.
Constraints
n == coins.length1 <= n <= 3 * 1040 <= coins[i] <= 1edges.length == n - 1edges[i].length == 20 <= ai, bi < nai != biedges represents a valid tree.How Interview Coder Helps with Leetcode Problems
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