Space Replacement详解编程语言

Write a method to replace all spaces in a string with %20.  
The string is given in a characters array, you can assume it has enough space  
for replacement and you are given the true length of the string. 
 
Example 
Given "Mr John Smith", length = 13. 
 
The string after replacement should be "Mr%20John%20Smith". 
 
Note 
If you are using Java or Python，please use characters array instead of string. 
 
Challenge 
Do it in-place.

public class Solution { 
    /** 
     * @param string: An array of Char 
     * @param length: The true length of the string 
     * @return: The true length of new string 
     */ 
    public int replaceBlank(char[] string, int length) { 
        if (string == null) return 0; 
 
        int space = 0; 
        for (char c : string) { 
            if (c == ' ') space++; 
        } 
 
        int r = length + 2 * space - 1; 
        for (int i = length - 1; i >= 0; i--) { 
            if (string[i] != ' ') { 
                string[r] = string[i]; 
                r--; 
            } else { 
                string[r--] = '0'; 
                string[r--] = '2'; 
                string[r--] = '%'; 
            } 
        } 
 
        return length + 2 * space; 
    } 
}