Given a nested list of integers, implement an iterator to flatten it.
Each element is either an integer, or a list – whose elements may also be integers or other lists. Input: [[1,1],2,[1,1]] Output: [1,1,2,1,1]
The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that "all houses in this place forms a binary tree". It will automatically contact the police if two directly-linked houses were broken into on the same night. Determine the maximum amount of money the thief can rob tonight without alerting the police.
Given n balloons, indexed from 0 to n-1. Each balloon is painted with a number on it represented by array nums. You are asked to burst all the balloons. If the you burst balloon i you will get nums[left] * nums[i] * nums[right] coins. Here left and right are adjacent indices of i. After the burst, the left and right then becomes adjacent. Find the maximum coins you can collect by bursting the balloons wisely. examples: nums = [3,1,5,8] --> [3,5,8] --> [3,8] -->  -->  coins = 3*1*5 + 3*5*8 + 1*3*8 + 1*8*1 = 167
- integers, symbols, cons cells,
- global variables,
- lexically-scoped local variables,
- if conditional,
- primitive functions, such as +, =, <, or list,
- user-defined functions,
- a macro system,
- and a copying garbage collector.
Given an integer matrix, find the length of the longest increasing path From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of the boundary (i.e. wrap-around is not allowed). example: nums = [ [9,9,4], [6,6,8], [2,1,1] ] return 4