Implement an algorithm to determine if a string has all unique characters. What if you cannot use additional datastructures?

Given two strings, write a method to decide if one is a permutation of the other.

Write a method to replace all spaces in a string with '%20'. You may assume that the string has sufficient space at the end to hold the additional characters, and that you are given the "true" length of the string. (Note: If implementing in Java, please use a character array so that you can perform this operation in place.)

Example

Input:  "Mr John Smith    ", 13
Output: "Mr%20John%20Smith"