OS process里的address space长什么样
1) Given a string, format this string to keep only one space between each word.
2) Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.
The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.
Follow up:The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).
3)Write a function that takes in a string and returns the length of the longest substring in which all characters are arranged in alphabetical order