Introduction

In this blog post, we'll share the most commonly asked coding interview questions at MathWorks. 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: Pass the Pillow

There are n people standing in a line labeled from 1 to n. The first person in the line is holding a pillow initially. Every second, the person holding the pillow passes it to the next person standing in the line. Once the pillow reaches the end of the line, the direction changes, and people continue passing the pillow in the opposite direction. For example, once the pillow reaches the nth person they pass it to the n - 1th person, then to the n - 2th person and so on. Given the two positive integers n and time, return the index of the person holding the pillow after time seconds. Example 1: Input: n = 4, time = 5 Output: 2 Explanation: People pass the pillow in the following way: 1 -> 2 -> 3 -> 4 -> 3 -> 2. After five seconds, the 2nd person is holding the pillow. Example 2: Input: n = 3, time = 2 Output: 3 Explanation: People pass the pillow in the following way: 1 -> 2 -> 3. After two seconds, the 3rd person is holding the pillow. Constraints: 2 <= n <= 1000 1 <= time <= 1000 Note: This question is the same as 3178: Find the Child Who Has the Ball After K Seconds.

Topics: Math, Simulation

Problem #2: Minimum Edge Reversals So Every Node Is Reachable

There is a simple directed graph with n nodes labeled from 0 to n - 1. The graph would form a tree if its edges were bi-directional. You are given an integer n and a 2D integer array edges, where edges[i] = [ui, vi] represents a directed edge going from node ui to node vi. An edge reversal changes the direction of an edge, i.e., a directed edge going from node ui to node vi becomes a directed edge going from node vi to node ui. For every node i in the range [0, n - 1], your task is to independently calculate the minimum number of edge reversals required so it is possible to reach any other node starting from node i through a sequence of directed edges. Return an integer array answer, where answer[i] is the minimum number of edge reversals required so it is possible to reach any other node starting from node i through a sequence of directed edges. Example 1: Input: n = 4, edges = [[2,0],[2,1],[1,3]] Output: [1,1,0,2] Explanation: The image above shows the graph formed by the edges. For node 0: after reversing the edge [2,0], it is possible to reach any other node starting from node 0. So, answer[0] = 1. For node 1: after reversing the edge [2,1], it is possible to reach any other node starting from node 1. So, answer[1] = 1. For node 2: it is already possible to reach any other node starting from node 2. So, answer[2] = 0. For node 3: after reversing the edges [1,3] and [2,1], it is possible to reach any other node starting from node 3. So, answer[3] = 2. Example 2: Input: n = 3, edges = [[1,2],[2,0]] Output: [2,0,1] Explanation: The image above shows the graph formed by the edges. For node 0: after reversing the edges [2,0] and [1,2], it is possible to reach any other node starting from node 0. So, answer[0] = 2. For node 1: it is already possible to reach any other node starting from node 1. So, answer[1] = 0. For node 2: after reversing the edge [1, 2], it is possible to reach any other node starting from node 2. So, answer[2] = 1. Constraints: 2 <= n <= 105 edges.length == n - 1 edges[i].length == 2 0 <= ui == edges[i][0] < n 0 <= vi == edges[i][1] < n ui != vi The input is generated such that if the edges were bi-directional, the graph would be a tree.

Topics: Dynamic Programming, Depth-First Search, Breadth-First Search, Graph

Problem #3: Count Subarrays With Fixed Bounds

You are given an integer array nums and two integers minK and maxK. A fixed-bound subarray of nums is a subarray that satisfies the following conditions: The minimum value in the subarray is equal to minK. The maximum value in the subarray is equal to maxK. Return the number of fixed-bound subarrays. A subarray is a contiguous part of an array. Example 1: Input: nums = [1,3,5,2,7,5], minK = 1, maxK = 5 Output: 2 Explanation: The fixed-bound subarrays are [1,3,5] and [1,3,5,2]. Example 2: Input: nums = [1,1,1,1], minK = 1, maxK = 1 Output: 10 Explanation: Every subarray of nums is a fixed-bound subarray. There are 10 possible subarrays. Constraints: 2 <= nums.length <= 105 1 <= nums[i], minK, maxK <= 106

Topics: Array, Queue, Sliding Window, Monotonic Queue

Problem #4: String Transformation

You are given two strings s and t of equal length n. You can perform the following operation on the string s: Remove a suffix of s of length l where 0 < l < n and append it at the start of s. For example, let s = 'abcd' then in one operation you can remove the suffix 'cd' and append it in front of s making s = 'cdab'. You are also given an integer k. Return the number of ways in which s can be transformed into t in exactly k operations. Since the answer can be large, return it modulo 109 + 7. Example 1: Input: s = "abcd", t = "cdab", k = 2 Output: 2 Explanation: First way: In first operation, choose suffix from index = 3, so resulting s = "dabc". In second operation, choose suffix from index = 3, so resulting s = "cdab". Second way: In first operation, choose suffix from index = 1, so resulting s = "bcda". In second operation, choose suffix from index = 1, so resulting s = "cdab". Example 2: Input: s = "ababab", t = "ababab", k = 1 Output: 2 Explanation: First way: Choose suffix from index = 2, so resulting s = "ababab". Second way: Choose suffix from index = 4, so resulting s = "ababab". Constraints: 2 <= s.length <= 5 * 105 1 <= k <= 1015 s.length == t.length s and t consist of only lowercase English alphabets.

Topics: Math, String, Dynamic Programming, String Matching