Introduction

In this blog post, we'll share the most commonly asked coding interview questions at Visa. 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: Length of Longest V-Shaped Diagonal Segment

You are given a 2D integer matrix grid of size n x m, where each element is either 0, 1, or 2. A V-shaped diagonal segment is defined as: The segment starts with 1. The subsequent elements follow this infinite sequence: 2, 0, 2, 0, .... The segment: Starts along a diagonal direction (top-left to bottom-right, bottom-right to top-left, top-right to bottom-left, or bottom-left to top-right). Continues the sequence in the same diagonal direction. Makes at most one clockwise 90-degree turn to another diagonal direction while maintaining the sequence. Return the length of the longest V-shaped diagonal segment. If no valid segment exists, return 0. Example 1: Input: grid = [[2,2,1,2,2],[2,0,2,2,0],[2,0,1,1,0],[1,0,2,2,2],[2,0,0,2,2]] Output: 5 Explanation: The longest V-shaped diagonal segment has a length of 5 and follows these coordinates: (0,2) → (1,3) → (2,4), takes a 90-degree clockwise turn at (2,4), and continues as (3,3) → (4,2). Example 2: Input: grid = [[2,2,2,2,2],[2,0,2,2,0],[2,0,1,1,0],[1,0,2,2,2],[2,0,0,2,2]] Output: 4 Explanation: The longest V-shaped diagonal segment has a length of 4 and follows these coordinates: (2,3) → (3,2), takes a 90-degree clockwise turn at (3,2), and continues as (2,1) → (1,0). Example 3: Input: grid = [[1,2,2,2,2],[2,2,2,2,0],[2,0,0,0,0],[0,0,2,2,2],[2,0,0,2,0]] Output: 5 Explanation: The longest V-shaped diagonal segment has a length of 5 and follows these coordinates: (0,0) → (1,1) → (2,2) → (3,3) → (4,4). Example 4: Input: grid = [[1]] Output: 1 Explanation: The longest V-shaped diagonal segment has a length of 1 and follows these coordinates: (0,0). Constraints: n == grid.length m == grid[i].length 1 <= n, m <= 500 grid[i][j] is either 0, 1 or 2.

Topics: Array, Dynamic Programming, Memoization, Matrix

Problem #2: Two Sum

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order. Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Explanation: Because nums[0] + nums[1] == 9, we return [0, 1]. Example 2: Input: nums = [3,2,4], target = 6 Output: [1,2] Example 3: Input: nums = [3,3], target = 6 Output: [0,1] Constraints: 2 <= nums.length <= 104 -109 <= nums[i] <= 109 -109 <= target <= 109 Only one valid answer exists. Follow-up: Can you come up with an algorithm that is less than O(n2) time complexity?

Topics: Array, Hash Table

Problem #3: Rotating the Box

You are given an m x n matrix of characters boxGrid representing a side-view of a box. Each cell of the box is one of the following: A stone '#' A stationary obstacle '' Empty '.' The box is rotated 90 degrees clockwise, causing some of the stones to fall due to gravity. Each stone falls down until it lands on an obstacle, another stone, or the bottom of the box. Gravity does not affect the obstacles' positions, and the inertia from the box's rotation does not affect the stones' horizontal positions. It is guaranteed that each stone in boxGrid rests on an obstacle, another stone, or the bottom of the box. Return an n x m matrix representing the box after the rotation described above. Example 1: Input: boxGrid = [["#",".","#"]] Output: [["."], ["#"], ["#"]] Example 2: Input: boxGrid = [["#",".","","."], ["#","#","","."]] Output: [["#","."], ["#","#"], ["",""], [".","."]] Example 3: Input: boxGrid = [["#","#","",".","","."], ["#","#","#","",".","."], ["#","#","#",".","#","."]] Output: [[".","#","#"], [".","#","#"], ["#","#",""], ["#","","."], ["#",".",""], ["#",".","."]] Constraints: m == boxGrid.length n == boxGrid[i].length 1 <= m, n <= 500 boxGrid[i][j] is either '#', '', or '.'.

Topics: Array, Two Pointers, Matrix

Problem #4: LRU Cache

Design a data structure that follows the constraints of a Least Recently Used (LRU) cache. Implement the LRUCache class: LRUCache(int capacity) Initialize the LRU cache with positive size capacity. int get(int key) Return the value of the key if the key exists, otherwise return -1. void put(int key, int value) Update the value of the key if the key exists. Otherwise, add the key-value pair to the cache. If the number of keys exceeds the capacity from this operation, evict the least recently used key. The functions get and put must each run in O(1) average time complexity. Example 1: Input ["LRUCache", "put", "put", "get", "put", "get", "put", "get", "get", "get"] [[2], [1, 1], [2, 2], [1], [3, 3], [2], [4, 4], [1], [3], [4]] Output [null, null, null, 1, null, -1, null, -1, 3, 4] Explanation LRUCache lRUCache = new LRUCache(2); lRUCache.put(1, 1); // cache is {1=1} lRUCache.put(2, 2); // cache is {1=1, 2=2} lRUCache.get(1); // return 1 lRUCache.put(3, 3); // LRU key was 2, evicts key 2, cache is {1=1, 3=3} lRUCache.get(2); // returns -1 (not found) lRUCache.put(4, 4); // LRU key was 1, evicts key 1, cache is {4=4, 3=3} lRUCache.get(1); // return -1 (not found) lRUCache.get(3); // return 3 lRUCache.get(4); // return 4 Constraints: 1 <= capacity <= 3000 0 <= key <= 104 0 <= value <= 105 At most 2 * 105 calls will be made to get and put.

Topics: Hash Table, Linked List, Design, Doubly-Linked List

Problem #5: 3Sum

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0. Notice that the solution set must not contain duplicate triplets. Example 1: Input: nums = [-1,0,1,2,-1,-4] Output: [[-1,-1,2],[-1,0,1]] Explanation: nums[0] + nums[1] + nums[2] = (-1) + 0 + 1 = 0. nums[1] + nums[2] + nums[4] = 0 + 1 + (-1) = 0. nums[0] + nums[3] + nums[4] = (-1) + 2 + (-1) = 0. The distinct triplets are [-1,0,1] and [-1,-1,2]. Notice that the order of the output and the order of the triplets does not matter. Example 2: Input: nums = [0,1,1] Output: [] Explanation: The only possible triplet does not sum up to 0. Example 3: Input: nums = [0,0,0] Output: [[0,0,0]] Explanation: The only possible triplet sums up to 0. Constraints: 3 <= nums.length <= 3000 -105 <= nums[i] <= 105

Topics: Array, Two Pointers, Sorting

Problem #6: Trapping Rain Water

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining. Example 1: Input: height = [0,1,0,2,1,0,1,3,2,1,2,1] Output: 6 Explanation: The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Example 2: Input: height = [4,2,0,3,2,5] Output: 9 Constraints: n == height.length 1 <= n <= 2 * 104 0 <= height[i] <= 105

Topics: Array, Two Pointers, Dynamic Programming, Stack, Monotonic Stack

Problem #7: Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type. Example 1: Input: s = "()" Output: true Example 2: Input: s = "()[]{}" Output: true Example 3: Input: s = "(]" Output: false Example 4: Input: s = "([])" Output: true Constraints: 1 <= s.length <= 104 s consists of parentheses only '()[]{}'.

Topics: String, Stack

Problem #8: Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string "". Example 1: Input: strs = ["flower","flow","flight"] Output: "fl" Example 2: Input: strs = ["dog","racecar","car"] Output: "" Explanation: There is no common prefix among the input strings. Constraints: 1 <= strs.length <= 200 0 <= strs[i].length <= 200 strs[i] consists of only lowercase English letters if it is non-empty.

Topics: String, Trie

Problem #9: Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

Given an array of integers nums and an integer limit, return the size of the longest non-empty subarray such that the absolute difference between any two elements of this subarray is less than or equal to limit. Example 1: Input: nums = [8,2,4,7], limit = 4 Output: 2 Explanation: All subarrays are: [8] with maximum absolute diff |8-8| = 0 <= 4. [8,2] with maximum absolute diff |8-2| = 6 > 4. [8,2,4] with maximum absolute diff |8-2| = 6 > 4. [8,2,4,7] with maximum absolute diff |8-2| = 6 > 4. [2] with maximum absolute diff |2-2| = 0 <= 4. [2,4] with maximum absolute diff |2-4| = 2 <= 4. [2,4,7] with maximum absolute diff |2-7| = 5 > 4. [4] with maximum absolute diff |4-4| = 0 <= 4. [4,7] with maximum absolute diff |4-7| = 3 <= 4. [7] with maximum absolute diff |7-7| = 0 <= 4. Therefore, the size of the longest subarray is 2. Example 2: Input: nums = [10,1,2,4,7,2], limit = 5 Output: 4 Explanation: The subarray [2,4,7,2] is the longest since the maximum absolute diff is |2-7| = 5 <= 5. Example 3: Input: nums = [4,2,2,2,4,4,2,2], limit = 0 Output: 3 Constraints: 1 <= nums.length <= 105 1 <= nums[i] <= 109 0 <= limit <= 109

Topics: Array, Queue, Sliding Window, Heap (Priority Queue), Ordered Set, Monotonic Queue

Problem #10: Text Justification

Given an array of strings words and a width maxWidth, format the text such that each line has exactly maxWidth characters and is fully (left and right) justified. You should pack your words in a greedy approach; that is, pack as many words as you can in each line. Pad extra spaces ' ' when necessary so that each line has exactly maxWidth characters. Extra spaces between words should be distributed as evenly as possible. If the number of spaces on a line does not divide evenly between words, the empty slots on the left will be assigned more spaces than the slots on the right. For the last line of text, it should be left-justified, and no extra space is inserted between words. Note: A word is defined as a character sequence consisting of non-space characters only. Each word's length is guaranteed to be greater than 0 and not exceed maxWidth. The input array words contains at least one word. Example 1: Input: words = ["This", "is", "an", "example", "of", "text", "justification."], maxWidth = 16 Output: [ "This is an", "example of text", "justification. " ] Example 2: Input: words = ["What","must","be","acknowledgment","shall","be"], maxWidth = 16 Output: [ "What must be", "acknowledgment ", "shall be " ] Explanation: Note that the last line is "shall be " instead of "shall be", because the last line must be left-justified instead of fully-justified. Note that the second line is also left-justified because it contains only one word. Example 3: Input: words = ["Science","is","what","we","understand","well","enough","to","explain","to","a","computer.","Art","is","everything","else","we","do"], maxWidth = 20 Output: [ "Science is what we", "understand well", "enough to explain to", "a computer. Art is", "everything else we", "do " ] Constraints: 1 <= words.length <= 300 1 <= words[i].length <= 20 words[i] consists of only English letters and symbols. 1 <= maxWidth <= 100 words[i].length <= maxWidth

Topics: Array, String, Simulation