Spiral Traversal

Medium

Return the elements of a matrix in clockwise spiral order.

Example:

Output: [0, 1, 2, 3, 4, 9, 14, 19, 18, 17, 16, 15, 10, 5, 6, 7, 8, 13, 12, 11]

Reverse 32-Bit Integer

Medium

Reverse the digits of a signed 32-bit integer. If the reversed integer overflows (i.e., is outside the range [−231−231, 231−1231−1]), return 0. Assume the environment only allows you to store integers within the signed 32-bit integer range.

Example 1:

Input: n = 420
Output: 24

Example 2:

Input: n = -15
Output: -51

Maximum Collinear Points

Hard

Given a set of points in a two-dimensional plane, determine the maximum number of points that lie along the same straight line.

Example:

Input: points = [[1, 1], [1, 3], [2, 2], [3, 1], [3, 3], [4, 4]]
Output: 4

Constraints:

• The input won’t contain duplicate points.

The Josephus Problem

Medium

There are n people standing in a circle, numbered from 0 to n - 1. Starting from person 0, count k people clockwise and remove the kth person. After the removal, begin counting again from the next person still in the circle. Repeat this process until only one person remains, and return that person’s position.

Example:

Input: n = 5, k = 2
Output: 2

Constraints:

• There will be at least one person in the circle
• k will at least be equal to 1.

Triangle Numbers

Medium

Consider a triangle composed of numbers where the top of the triangle is 1. Each subsequent number in the triangle is equal to the sum of three numbers above it: its top-left number, its top number, and its top-right number. If any of these three numbers don’t exist, assume they are equal to 0.

Given a value representing a row of this triangle, return the position of the first even number in this row. Assume that the first number in each row is at position 1.

Example:

Input: n = 4
Output: 3

Constraints:

• n will be at least 3.