Introduction

In this blog post, we'll share the most commonly asked coding interview questions at Geico. 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 #2: Largest Palindromic Number

You are given a string num consisting of digits only. Return the largest palindromic integer (in the form of a string) that can be formed using digits taken from num. It should not contain leading zeroes. Notes: You do not need to use all the digits of num, but you must use at least one digit. The digits can be reordered. Example 1: Input: num = "444947137" Output: "7449447" Explanation: Use the digits "4449477" from "444947137" to form the palindromic integer "7449447". It can be shown that "7449447" is the largest palindromic integer that can be formed. Example 2: Input: num = "00009" Output: "9" Explanation: It can be shown that "9" is the largest palindromic integer that can be formed. Note that the integer returned should not contain leading zeroes. Constraints: 1 <= num.length <= 105 num consists of digits.

Topics: Hash Table, String, Greedy, Counting

Problem #3: Number of Steps to Reduce a Number in Binary Representation to One

Given the binary representation of an integer as a string s, return the number of steps to reduce it to 1 under the following rules: If the current number is even, you have to divide it by 2. If the current number is odd, you have to add 1 to it. It is guaranteed that you can always reach one for all test cases. Example 1: Input: s = "1101" Output: 6 Explanation: "1101" corressponds to number 13 in their decimal representation. Step 1) 13 is odd, add 1 and obtain 14. Step 2) 14 is even, divide by 2 and obtain 7. Step 3) 7 is odd, add 1 and obtain 8. Step 4) 8 is even, divide by 2 and obtain 4. Step 5) 4 is even, divide by 2 and obtain 2. Step 6) 2 is even, divide by 2 and obtain 1. Example 2: Input: s = "10" Output: 1 Explanation: "10" corresponds to number 2 in their decimal representation. Step 1) 2 is even, divide by 2 and obtain 1. Example 3: Input: s = "1" Output: 0 Constraints: 1 <= s.length <= 500 s consists of characters '0' or '1' s[0] == '1'

Topics: String, Bit Manipulation

Problem #4: Coin Change

You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money. Return the fewest number of coins that you need to make up that amount. If that amount of money cannot be made up by any combination of the coins, return -1. You may assume that you have an infinite number of each kind of coin. Example 1: Input: coins = [1,2,5], amount = 11 Output: 3 Explanation: 11 = 5 + 5 + 1 Example 2: Input: coins = [2], amount = 3 Output: -1 Example 3: Input: coins = [1], amount = 0 Output: 0 Constraints: 1 <= coins.length <= 12 1 <= coins[i] <= 231 - 1 0 <= amount <= 104

Topics: Array, Dynamic Programming, Breadth-First Search

Problem #5: Best Time to Buy and Sell Stock with Cooldown

You are given an array prices where prices[i] is the price of a given stock on the ith day. Find the maximum profit you can achieve. You may complete as many transactions as you like (i.e., buy one and sell one share of the stock multiple times) with the following restrictions: After you sell your stock, you cannot buy stock on the next day (i.e., cooldown one day). Note: You may not engage in multiple transactions simultaneously (i.e., you must sell the stock before you buy again). Example 1: Input: prices = [1,2,3,0,2] Output: 3 Explanation: transactions = [buy, sell, cooldown, buy, sell] Example 2: Input: prices = [1] Output: 0 Constraints: 1 <= prices.length <= 5000 0 <= prices[i] <= 1000

Topics: Array, Dynamic Programming

Problem #7: First Missing Positive

Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums. You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space. Example 1: Input: nums = [1,2,0] Output: 3 Explanation: The numbers in the range [1,2] are all in the array. Example 2: Input: nums = [3,4,-1,1] Output: 2 Explanation: 1 is in the array but 2 is missing. Example 3: Input: nums = [7,8,9,11,12] Output: 1 Explanation: The smallest positive integer 1 is missing. Constraints: 1 <= nums.length <= 105 -231 <= nums[i] <= 231 - 1

Topics: Array, Hash Table

Problem #8: Best Time to Buy and Sell Stock II

You are given an integer array prices where prices[i] is the price of a given stock on the ith day. On each day, you may decide to buy and/or sell the stock. You can only hold at most one share of the stock at any time. However, you can buy it then immediately sell it on the same day. Find and return the maximum profit you can achieve. Example 1: Input: prices = [7,1,5,3,6,4] Output: 7 Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4. Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3. Total profit is 4 + 3 = 7. Example 2: Input: prices = [1,2,3,4,5] Output: 4 Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4. Total profit is 4. Example 3: Input: prices = [7,6,4,3,1] Output: 0 Explanation: There is no way to make a positive profit, so we never buy the stock to achieve the maximum profit of 0. Constraints: 1 <= prices.length <= 3 * 104 0 <= prices[i] <= 104

Topics: Array, Dynamic Programming, Greedy