322. 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. ...
328. Odd Even Linked List Given the head of a singly linked list, group all the nodes with odd indices together followed by the nodes with even indices, and return the reordered list. The first node is considered odd, and the second node is even, and so on. Note that the relative order inside both the even and odd groups should remain as it was in the input. Example 1: Input: head = [1,2,3,4,5] Output: [1,3,5,2,4] ...
91. Decode Ways 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”. ...
276. Paint Fence You are painting a fence of n posts with k different colors. You must paint the posts following these rules: Every post must be painted exactly one color. At most one pair of adjacent fence posts can have the same color. Given the two integers n and k, return the number of ways you can paint the fence. Example 1: Input: n = 3, k = 2 Output: 6 Explanation: All the possibilities are shown. Note that painting all the posts red or all the posts green is invalid because there can only be at most one pair of adjacent posts that are the same color. Example 2: Input: n = 1, k = 1 Output: 1 Example 3: Input: n = 7, k = 2 Output: 42 ...
63. Unique Paths II A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below). Now consider if some obstacles are added to the grids. How many unique paths would there be? ...
64. Minimum Path Sum Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right, which minimizes the sum of all numbers along its path. Note: You can only move either down or right at any point in time. Example 1: Input: grid = [[1,3,1],[1,5,1],[4,2,1]] Output: 7 Explanation: Because the path 1 → 3 → 1 → 1 → 1 minimizes the sum. ...
1859. Sorting the Sentence A sentence is a list of words that are separated by a single space with no leading or trailing spaces. Each word consists of lowercase and uppercase English letters. A sentence can be shuffled by appending the 1-indexed word position to each word then rearranging the words in the sentence. For example, the sentence “This is a sentence” can be shuffled as “sentence4 a3 is2 This1” or “is2 sentence4 This1 a3”. Given a shuffled sentence s containing no more than 9 words, reconstruct and return the original sentence. ...
1860. Incremental Memory Leak You are given two integers memory1 and memory2 representing the available memory in bits on two memory sticks. There is currently a faulty program running that consumes an increasing amount of memory every second. At the ith second (starting from 1), i bits of memory are allocated to the stick with more available memory (or from the first memory stick if both have the same available memory). If neither stick has at least i bits of available memory, the program crashes. ...
1861. Rotating the Box You are given an m x n matrix of characters box 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. ...
198. House Robber You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security systems connected and it will automatically contact the police if two adjacent houses were broken into on the same night. Given an integer array nums representing the amount of money of each house, return the maximum amount of money you can rob tonight without alerting the police. ...