Introduction

In this blog post, we'll share the most commonly asked coding interview questions at thoughtspot. If you don't have months to study for your interviews, you can use AI tools like Chatmagic to generate solutions quickly and efficiently - helping you pass the interviews and get the job offer!

Problem #1: Count Paths That Can Form a Palindrome in a Tree

You are given a tree (i.e. a connected, undirected graph that has no cycles) rooted at node 0 consisting of n nodes numbered from 0 to n - 1. The tree is represented by a 0-indexed array parent of size n, where parent[i] is the parent of node i. Since node 0 is the root, parent[0] == -1. You are also given a string s of length n, where s[i] is the character assigned to the edge between i and parent[i]. s[0] can be ignored. Return the number of pairs of nodes (u, v) such that u < v and the characters assigned to edges on the path from u to v can be rearranged to form a palindrome. A string is a palindrome when it reads the same backwards as forwards. Example 1: Input: parent = [-1,0,0,1,1,2], s = "acaabc" Output: 8 Explanation: The valid pairs are: - All the pairs (0,1), (0,2), (1,3), (1,4) and (2,5) result in one character which is always a palindrome. - The pair (2,3) result in the string "aca" which is a palindrome. - The pair (1,5) result in the string "cac" which is a palindrome. - The pair (3,5) result in the string "acac" which can be rearranged into the palindrome "acca". Example 2: Input: parent = [-1,0,0,0,0], s = "aaaaa" Output: 10 Explanation: Any pair of nodes (u,v) where u < v is valid. Constraints: n == parent.length == s.length 1 <= n <= 105 0 <= parent[i] <= n - 1 for all i >= 1 parent[0] == -1 parent represents a valid tree. s consists of only lowercase English letters.

Topics: Dynamic Programming, Bit Manipulation, Tree, Depth-First Search, Bitmask

Problem #2: Count Pairs of Connectable Servers in a Weighted Tree Network

You are given an unrooted weighted tree with n vertices representing servers numbered from 0 to n - 1, an array edges where edges[i] = [ai, bi, weighti] represents a bidirectional edge between vertices ai and bi of weight weighti. You are also given an integer signalSpeed. Two servers a and b are connectable through a server c if: a < b, a != c and b != c. The distance from c to a is divisible by signalSpeed. The distance from c to b is divisible by signalSpeed. The path from c to b and the path from c to a do not share any edges. Return an integer array count of length n where count[i] is the number of server pairs that are connectable through the server i. Example 1: Input: edges = [[0,1,1],[1,2,5],[2,3,13],[3,4,9],[4,5,2]], signalSpeed = 1 Output: [0,4,6,6,4,0] Explanation: Since signalSpeed is 1, count[c] is equal to the number of pairs of paths that start at c and do not share any edges. In the case of the given path graph, count[c] is equal to the number of servers to the left of c multiplied by the servers to the right of c. Example 2: Input: edges = [[0,6,3],[6,5,3],[0,3,1],[3,2,7],[3,1,6],[3,4,2]], signalSpeed = 3 Output: [2,0,0,0,0,0,2] Explanation: Through server 0, there are 2 pairs of connectable servers: (4, 5) and (4, 6). Through server 6, there are 2 pairs of connectable servers: (4, 5) and (0, 5). It can be shown that no two servers are connectable through servers other than 0 and 6. Constraints: 2 <= n <= 1000 edges.length == n - 1 edges[i].length == 3 0 <= ai, bi < n edges[i] = [ai, bi, weighti] 1 <= weighti <= 106 1 <= signalSpeed <= 106 The input is generated such that edges represents a valid tree.

Topics: Array, Tree, Depth-First Search