• Backtracking

  79. Word Search 39. Combination Sum

Problem description:

On an N x N board, the numbers from 1 to N*N are written boustrophedonically starting from the bottom left of the board, and alternating direction each row. For example, for a 6 x 6 board, the numbers are written as follows:

Thread vs Process

• Definition
  A process is an instance of a computer program that is being executed. It contains the program code and its current activity. A process may be made up of multiple threads of execution that execute instructions concurrently. A process has a virtual address space, executable code, open handles to system objects, a security context, a unique process identifier, environment variables, a priority class, minimum and maximum working set sizes, and at least one thread of execution. Each process is started with a single thread, often called the primary thread, but can create additional threads from any of its threads.

Problem description:

There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direct friend of C, then A is an indirect friend of C. And we defined a friend circle is a group of students who are direct or indirect friends.

Problem description:

Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, …) which sum to n.

Problem description:

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

Problem description:

Given a circular array C of integers represented by A, find the maximum possible sum of a non-empty subarray of C.

Problem description:

Design a max stack that supports push, pop, top, peekMax and popMax.

Problem description:

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

Problem description:

Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element.