Implement FreqStack, a class which simulates the operation of a stack-like data structure.
FreqStack has two functions:
- push(int x), which pushes an integer x onto the stack.
- pop(), which removes and returns the most frequent element in the stack.
- If there is a tie for most frequent element, the element closest to the top of the stack is removed and returned.
Suppose you are at a party with n people (labeled from 0 to n - 1), and among them, there may exist one celebrity. The definition of a celebrity is that all the other n - 1 people know him/her, but he/she does not know any of them.
Now you want to find out who the celebrity is or verify that there is not one. The only thing you are allowed to do is to ask questions like: “Hi, A. Do you know B?” to get information about whether A knows B. You need to find out the celebrity (or verify there is not one) by asking as few questions as possible (in the asymptotic sense).
You are given a helper function bool knows(a, b) which tells you whether A knows B. Implement a function int findCelebrity(n). There will be exactly one celebrity if he/she is in the party. Return the celebrity’s label if there is a celebrity in the party. If there is no celebrity, return -1.
1773. Count Items Matching a Rule
You are given an array items, where each items[i] = [typei, colori, namei] describes the type, color, and name of the ith item. You are also given a rule represented by two strings, ruleKey and ruleValue.
The ith item is said to match the rule if one of the following is true:
- ruleKey == “type” and ruleValue == typei.
- ruleKey == “color” and ruleValue == colori.
- ruleKey == “name” and ruleValue == namei.
Return the number of items that match the given rule.
You would like to make dessert and are preparing to buy the ingredients. You have n ice cream base flavors and m types of toppings to choose from. You must follow these rules when making your dessert:
- There must be exactly one ice cream base.
- You can add one or more types of topping or have no toppings at all.
- There are at most two of each type of topping.
You are given three inputs:
- baseCosts, an integer array of length n, where each baseCosts[i] represents the price of the ith ice cream base flavor.
- toppingCosts, an integer array of length m, where each toppingCosts[i] is the price of one of the ith topping.
- target, an integer representing your target price for dessert.
You want to make a dessert with a total cost as close to target as possible.
Return the closest possible cost of the dessert to target. If there are multiple, return the lower one.
There are n cars traveling at different speeds in the same direction along a one-lane road. You are given an array cars of length n, where cars[i] = [positioni, speedi] represents:
- positioni is the distance between the ith car and the beginning of the road in meters. It is guaranteed that positioni < positioni+1.
- speedi is the initial speed of the ith car in meters per second.
For simplicity, cars can be considered as points moving along the number line. Two cars collide when they occupy the same position. Once a car collides with another car, they unite and form a single car fleet. The cars in the formed fleet will have the same position and the same speed, which is the initial speed of the slowest car in the fleet.
Return an array answer, where answer[i] is the time, in seconds, at which the ith car collides with the next car, or -1 if the car does not collide with the next car. Answers within 10-5 of the actual answers are accepted.
1775. Equal Sum Arrays With Minimum Number of Operations
You are given two arrays of integers nums1 and nums2, possibly of different lengths. The values in the arrays are between 1 and 6, inclusive.
In one operation, you can change any integer’s value in any of the arrays to any value between 1 and 6, inclusive.
Return the minimum number of operations required to make the sum of values in nums1 equal to the sum of values in nums2. Return -1 if it is not possible to make the sum of the two arrays equal.
A message containing letters from A-Z can be encoded into numbers using the following mapping:
>‘A’ -> “1”
‘B’ -> “2”
…
‘Z’ -> “26”
To decode an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping above (there may be multiple ways). For example, “11106” can be mapped into:
- “AAJF” with the grouping (1 1 10 6)
- “KJF” with the grouping (11 10 6)
Note that the grouping (1 11 06) is invalid because “06” cannot be mapped into ‘F’ since “6” is different from “06”.
Given a string s containing only digits, return the number of ways to decode it.
The answer is guaranteed to fit in a 32-bit integer.
Winter is coming! During the contest, your first job is to design a standard heater with a fixed warm radius to warm all the houses.
Every house can be warmed, as long as the house is within the heater’s warm radius range.
Given the positions of houses and heaters on a horizontal line, return the minimum radius standard of heaters so that those heaters could cover all houses.
Notice that all the heaters follow your radius standard, and the warm radius will the same.
81. Search in Rotated Sorted Array II
There is an integer array nums sorted in non-decreasing order (not necessarily with distinct values).
Before being passed to your function, nums is rotated at an unknown pivot index k (0 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], …, nums[n-1], nums[0], nums[1], …, nums[k-1]] (0-indexed). For example, [0,1,2,4,4,4,5,6,6,7] might be rotated at pivot index 5 and become [4,5,6,6,7,0,1,2,4,4].
Given the array nums after the rotation and an integer target, return true if target is in nums, or false if it is not in nums.
Given a positive integer n, find the smallest integer which has exactly the same digits existing in the integer n and is greater in value than n. If no such positive integer exists, return -1.
Note that the returned integer should fit in 32-bit integer, if there is a valid answer but it does not fit in 32-bit integer, return -1.