Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, …) which sum to n. ExampleNo.1Input: n = 12 Out ...

Count the number of prime numbers less than a non-negative number, n. ExampleInput: 10 Output: 4 Explanation: There are 4 prime numbers less than 10, ...

A quadtree is a tree data in which each internal node has exactly four children: topLeft, topRight, bottomLeft and bottomRight. Quad trees are often u ...

We want to use quad trees to store an N x N boolean grid. Each cell in the grid can only be true or false. The root node represents the whole grid. Fo ...

Give a string s, count the number of non-empty (contiguous) substrings that have the same number of 0’s and 1’s, and all the 0’s and all the 1’s in th ...

Your are given an array of integers prices, for which the i-th element is the price of a given stock on day i; and a non-negative integer fee represen ...

Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may comple ...

Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may comple ...

Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction ...

Given a binary tree, determine if it is a complete binary tree. Definition of a complete binary tree from Wikipedia:In a complete binary tree every le ...