Introduction

In this blog post, we'll share the most commonly asked coding interview questions at Swiggy. 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: Integer to Roman

Seven different symbols represent Roman numerals with the following values: Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 Roman numerals are formed by appending the conversions of decimal place values from highest to lowest. Converting a decimal place value into a Roman numeral has the following rules: If the value does not start with 4 or 9, select the symbol of the maximal value that can be subtracted from the input, append that symbol to the result, subtract its value, and convert the remainder to a Roman numeral. If the value starts with 4 or 9 use the subtractive form representing one symbol subtracted from the following symbol, for example, 4 is 1 (I) less than 5 (V): IV and 9 is 1 (I) less than 10 (X): IX. Only the following subtractive forms are used: 4 (IV), 9 (IX), 40 (XL), 90 (XC), 400 (CD) and 900 (CM). Only powers of 10 (I, X, C, M) can be appended consecutively at most 3 times to represent multiples of 10. You cannot append 5 (V), 50 (L), or 500 (D) multiple times. If you need to append a symbol 4 times use the subtractive form. Given an integer, convert it to a Roman numeral. Example 1: Input: num = 3749 Output: "MMMDCCXLIX" Explanation: 3000 = MMM as 1000 (M) + 1000 (M) + 1000 (M) 700 = DCC as 500 (D) + 100 (C) + 100 (C) 40 = XL as 10 (X) less of 50 (L) 9 = IX as 1 (I) less of 10 (X) Note: 49 is not 1 (I) less of 50 (L) because the conversion is based on decimal places Example 2: Input: num = 58 Output: "LVIII" Explanation: 50 = L 8 = VIII Example 3: Input: num = 1994 Output: "MCMXCIV" Explanation: 1000 = M 900 = CM 90 = XC 4 = IV Constraints: 1 <= num <= 3999

Topics: Hash Table, Math, String

Problem #2: Count Good Meals

A good meal is a meal that contains exactly two different food items with a sum of deliciousness equal to a power of two. You can pick any two different foods to make a good meal. Given an array of integers deliciousness where deliciousness[i] is the deliciousness of the i​​​​​​th​​​​​​​​ item of food, return the number of different good meals you can make from this list modulo 109 + 7. Note that items with different indices are considered different even if they have the same deliciousness value. Example 1: Input: deliciousness = [1,3,5,7,9] Output: 4 Explanation: The good meals are (1,3), (1,7), (3,5) and, (7,9). Their respective sums are 4, 8, 8, and 16, all of which are powers of 2. Example 2: Input: deliciousness = [1,1,1,3,3,3,7] Output: 15 Explanation: The good meals are (1,1) with 3 ways, (1,3) with 9 ways, and (1,7) with 3 ways. Constraints: 1 <= deliciousness.length <= 105 0 <= deliciousness[i] <= 220

Topics: Array, Hash Table

Problem #3: Next Greater Element I

The next greater element of some element x in an array is the first greater element that is to the right of x in the same array. You are given two distinct 0-indexed integer arrays nums1 and nums2, where nums1 is a subset of nums2. For each 0 <= i < nums1.length, find the index j such that nums1[i] == nums2[j] and determine the next greater element of nums2[j] in nums2. If there is no next greater element, then the answer for this query is -1. Return an array ans of length nums1.length such that ans[i] is the next greater element as described above. Example 1: Input: nums1 = [4,1,2], nums2 = [1,3,4,2] Output: [-1,3,-1] Explanation: The next greater element for each value of nums1 is as follows: - 4 is underlined in nums2 = [1,3,4,2]. There is no next greater element, so the answer is -1. - 1 is underlined in nums2 = [1,3,4,2]. The next greater element is 3. - 2 is underlined in nums2 = [1,3,4,2]. There is no next greater element, so the answer is -1. Example 2: Input: nums1 = [2,4], nums2 = [1,2,3,4] Output: [3,-1] Explanation: The next greater element for each value of nums1 is as follows: - 2 is underlined in nums2 = [1,2,3,4]. The next greater element is 3. - 4 is underlined in nums2 = [1,2,3,4]. There is no next greater element, so the answer is -1. Constraints: 1 <= nums1.length <= nums2.length <= 1000 0 <= nums1[i], nums2[i] <= 104 All integers in nums1 and nums2 are unique. All the integers of nums1 also appear in nums2. Follow up: Could you find an O(nums1.length + nums2.length) solution?

Topics: Array, Hash Table, Stack, Monotonic Stack

Problem #4: Happy Number

Write an algorithm to determine if a number n is happy. A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits. Repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy. Return true if n is a happy number, and false if not. Example 1: Input: n = 19 Output: true Explanation: 12 + 92 = 82 82 + 22 = 68 62 + 82 = 100 12 + 02 + 02 = 1 Example 2: Input: n = 2 Output: false Constraints: 1 <= n <= 231 - 1

Topics: Hash Table, Math, Two Pointers

Problem #5: Fair Candy Swap

Alice and Bob have a different total number of candies. You are given two integer arrays aliceSizes and bobSizes where aliceSizes[i] is the number of candies of the ith box of candy that Alice has and bobSizes[j] is the number of candies of the jth box of candy that Bob has. Since they are friends, they would like to exchange one candy box each so that after the exchange, they both have the same total amount of candy. The total amount of candy a person has is the sum of the number of candies in each box they have. Return an integer array answer where answer[0] is the number of candies in the box that Alice must exchange, and answer[1] is the number of candies in the box that Bob must exchange. If there are multiple answers, you may return any one of them. It is guaranteed that at least one answer exists. Example 1: Input: aliceSizes = [1,1], bobSizes = [2,2] Output: [1,2] Example 2: Input: aliceSizes = [1,2], bobSizes = [2,3] Output: [1,2] Example 3: Input: aliceSizes = [2], bobSizes = [1,3] Output: [2,3] Constraints: 1 <= aliceSizes.length, bobSizes.length <= 104 1 <= aliceSizes[i], bobSizes[j] <= 105 Alice and Bob have a different total number of candies. There will be at least one valid answer for the given input.

Topics: Array, Hash Table, Binary Search, Sorting

Problem #6: Subarray Sum Equals K

Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k. A subarray is a contiguous non-empty sequence of elements within an array. Example 1: Input: nums = [1,1,1], k = 2 Output: 2 Example 2: Input: nums = [1,2,3], k = 3 Output: 2 Constraints: 1 <= nums.length <= 2 * 104 -1000 <= nums[i] <= 1000 -107 <= k <= 107

Topics: Array, Hash Table, Prefix Sum

Problem #7: Immediate Food Delivery II

Table: Delivery +-----------------------------+---------+ | Column Name | Type | +-----------------------------+---------+ | delivery_id | int | | customer_id | int | | order_date | date | | customer_pref_delivery_date | date | +-----------------------------+---------+ delivery_id is the column of unique values of this table. The table holds information about food delivery to customers that make orders at some date and specify a preferred delivery date (on the same order date or after it). If the customer's preferred delivery date is the same as the order date, then the order is called immediate; otherwise, it is called scheduled. The first order of a customer is the order with the earliest order date that the customer made. It is guaranteed that a customer has precisely one first order. Write a solution to find the percentage of immediate orders in the first orders of all customers, rounded to 2 decimal places. The result format is in the following example. Example 1: Input: Delivery table: +-------------+-------------+------------+-----------------------------+ | delivery_id | customer_id | order_date | customer_pref_delivery_date | +-------------+-------------+------------+-----------------------------+ | 1 | 1 | 2019-08-01 | 2019-08-02 | | 2 | 2 | 2019-08-02 | 2019-08-02 | | 3 | 1 | 2019-08-11 | 2019-08-12 | | 4 | 3 | 2019-08-24 | 2019-08-24 | | 5 | 3 | 2019-08-21 | 2019-08-22 | | 6 | 2 | 2019-08-11 | 2019-08-13 | | 7 | 4 | 2019-08-09 | 2019-08-09 | +-------------+-------------+------------+-----------------------------+ Output: +----------------------+ | immediate_percentage | +----------------------+ | 50.00 | +----------------------+ Explanation: The customer id 1 has a first order with delivery id 1 and it is scheduled. The customer id 2 has a first order with delivery id 2 and it is immediate. The customer id 3 has a first order with delivery id 5 and it is scheduled. The customer id 4 has a first order with delivery id 7 and it is immediate. Hence, half the customers have immediate first orders.

Topics: Database

Problem #8: Daily Temperatures

Given an array of integers temperatures represents the daily temperatures, return an array answer such that answer[i] is the number of days you have to wait after the ith day to get a warmer temperature. If there is no future day for which this is possible, keep answer[i] == 0 instead. Example 1: Input: temperatures = [73,74,75,71,69,72,76,73] Output: [1,1,4,2,1,1,0,0] Example 2: Input: temperatures = [30,40,50,60] Output: [1,1,1,0] Example 3: Input: temperatures = [30,60,90] Output: [1,1,0] Constraints: 1 <= temperatures.length <= 105 30 <= temperatures[i] <= 100

Topics: Array, Stack, Monotonic Stack

Problem #9: Maximum Score From Removing Substrings

You are given a string s and two integers x and y. You can perform two types of operations any number of times. Remove substring "ab" and gain x points. For example, when removing "ab" from "cabxbae" it becomes "cxbae". Remove substring "ba" and gain y points. For example, when removing "ba" from "cabxbae" it becomes "cabxe". Return the maximum points you can gain after applying the above operations on s. Example 1: Input: s = "cdbcbbaaabab", x = 4, y = 5 Output: 19 Explanation: - Remove the "ba" underlined in "cdbcbbaaabab". Now, s = "cdbcbbaaab" and 5 points are added to the score. - Remove the "ab" underlined in "cdbcbbaaab". Now, s = "cdbcbbaa" and 4 points are added to the score. - Remove the "ba" underlined in "cdbcbbaa". Now, s = "cdbcba" and 5 points are added to the score. - Remove the "ba" underlined in "cdbcba". Now, s = "cdbc" and 5 points are added to the score. Total score = 5 + 4 + 5 + 5 = 19. Example 2: Input: s = "aabbaaxybbaabb", x = 5, y = 4 Output: 20 Constraints: 1 <= s.length <= 105 1 <= x, y <= 104 s consists of lowercase English letters.

Topics: String, Stack, Greedy

Problem #10: Course Schedule

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, bi] indicates that you must take course bi first if you want to take course ai. For example, the pair [0, 1], indicates that to take course 0 you have to first take course 1. Return true if you can finish all courses. Otherwise, return false. Example 1: Input: numCourses = 2, prerequisites = [[1,0]] Output: true Explanation: There are a total of 2 courses to take. To take course 1 you should have finished course 0. So it is possible. Example 2: Input: numCourses = 2, prerequisites = [[1,0],[0,1]] Output: false Explanation: There are a total of 2 courses to take. To take course 1 you should have finished course 0, and to take course 0 you should also have finished course 1. So it is impossible. Constraints: 1 <= numCourses <= 2000 0 <= prerequisites.length <= 5000 prerequisites[i].length == 2 0 <= ai, bi < numCourses All the pairs prerequisites[i] are unique.

Topics: Depth-First Search, Breadth-First Search, Graph, Topological Sort