<p>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.)</p>
<p><strong>Example 1:</strong></p>
<pre>
<strong>Input: </strong>"Mr John Smith ", 13