There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings.
You are giving candies to these children subjected to the following requirements:
- Each child must have at least one candy.
- Children with a higher rating get more candies than their neighbors.
Return the minimum number of candies you need to have to distribute the candies to the children.
1913. Maximum Product Difference Between Two Pairs
The product difference between two pairs (a, b) and (c, d) is defined as (a b) - (c d).
- For example, the product difference between (5, 6) and (2, 7) is (5 6) - (2 7) = 16.
Given an integer array nums, choose four distinct indices w, x, y, and z such that the product difference between pairs (nums[w], nums[x]) and (nums[y], nums[z]) is maximized.
Return the maximum such product difference.
1914. Cyclically Rotating a Grid
You are given an m x n integer matrix grid, where m and n are both even integers, and an integer k.
The matrix is composed of several layers, which is shown in the below image, where each color is its own layer:
A cyclic rotation of the matrix is done by cyclically rotating each layer in the matrix. To cyclically rotate a layer once, each element in the layer will take the place of the adjacent element in the counter-clockwise direction. An example rotation is shown below:
Return the matrix after applying k cyclic rotations to it.
1915. Number of Wonderful Substrings
A wonderful string is a string where at most one letter appears an odd number of times.
- For example, “ccjjc” and “abab” are wonderful, but “ab” is not.
Given a string word that consists of the first ten lowercase English letters (‘a’ through ‘j’), return the number of wonderful non-empty substrings in word. If the same substring appears multiple times in word, then count each occurrence separately.
A substring is a contiguous sequence of characters in a string.
1916. Count Ways to Build Rooms in an Ant Colony
You are an ant tasked with adding n new rooms numbered 0 to n-1 to your colony. You are given the expansion plan as a 0-indexed integer array of length n, prevRoom, where prevRoom[i] indicates that you must build room prevRoom[i] before building room i, and these two rooms must be connected directly. Room 0 is already built, so prevRoom[0] = -1. The expansion plan is given such that once all the rooms are built, every room will be reachable from room 0.
You can only build one room at a time, and you can travel freely between rooms you have already built only if they are connected. You can choose to build any room as long as its previous room is already built.
Return the number of different orders you can build all the rooms in. Since the answer may be large, return it modulo 109 + 7.
Given a robot cleaner in a room modeled as a grid.
Each cell in the grid can be empty or blocked.
The robot cleaner with 4 given APIs can move forward, turn left or turn right. Each turn it made is 90 degrees.
When it tries to move into a blocked cell, its bumper sensor detects the obstacle and it stays on the current cell.
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interface Robot {
// returns true if next cell is open and robot moves into the cell.
// returns false if next cell is obstacle and robot stays on the current cell.
boolean move();
// Robot will stay on the same cell after calling turnLeft/turnRight.
// Each turn will be 90 degrees.
void turnLeft();
void turnRight();
// Clean the current cell.
void clean();
}Notes:
- The input is only given to initialize the room and the robot’s position internally. You must solve this problem “blindfolded”. In other words, you must control the robot using only the mentioned 4 APIs, without knowing the room layout and the initial robot’s position.
- The robot’s initial position will always be in an accessible cell.
- The initial direction of the robot will be facing up.
- All accessible cells are connected, which means the all cells marked as 1 will be accessible by the robot.
- Assume all four edges of the grid are all surrounded by wall.
431. Encode N-ary Tree to Binary Tree
Design an algorithm to encode an N-ary tree into a binary tree and decode the binary tree to get the original N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. Similarly, a binary tree is a rooted tree in which each node has no more than 2 children. There is no restriction on how your encode/decode algorithm should work. You just need to ensure that an N-ary tree can be encoded to a binary tree and this binary tree can be decoded to the original N-nary tree structure.
Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See following example).
For example, you may encode the following 3-ary tree to a binary tree in this way:
Note that the above is just an example which might or might not work. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.
On a 2-dimensional grid, there are 4 types of squares:
- 1 represents the starting square. There is exactly one starting square.
- 2 represents the ending square. There is exactly one ending square.
- 0 represents empty squares we can walk over.
- -1 represents obstacles that we cannot walk over.
Return the number of 4-directional walks from the starting square to the ending square, that walk over every non-obstacle square exactly once.
The chess knight has a unique movement, it may move two squares vertically and one square horizontally, or two squares horizontally and one square vertically (with both forming the shape of an L). The possible movements of chess knight are shown in this diagaram:
A chess knight can move as indicated in the chess diagram below:
We have a chess knight and a phone pad as shown below, the knight can only stand on a numeric cell (i.e. blue cell).
Given an integer n, return how many distinct phone numbers of length n we can dial.
You are allowed to place the knight on any numeric cell initially and then you should perform n - 1 jumps to dial a number of length n. All jumps should be valid knight jumps.
As the answer may be very large, return the answer modulo 109 + 7.
1277. Count Square Submatrices with All Ones
Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.
