Sword finger offer 05 Replace spaces

subject ：

Please implement a function , Put the string s Replace each space in with "%20".

Example 1：

Input ：s = "We are happy."
Output ："We%20are%20happy."

Limit ：

0 <= s The length of <= 10000

Ideas ：

1. Go through the first time , Check the number of spaces , Spaces need to be replaced with “%20”, Therefore, the array needs to be expanded .array.length - count + count * 3 Is the size of the array after replacement .

2. Copy from front to back .

class Solution {
    public String replaceSpace(String s) {
        if (s == null){
            return null;
        }

        char[] array = s.toCharArray();
        int count = 0;
        for (char c : array){
            if (c == ' '){
                count++;
            }
        }

        char[] newArray = new char[array.length - count + count * 3];
        int pointer = newArray.length - 1;
        for (int j = array.length - 1; j >= 0; j--){
            if (array[j] != ' '){
                newArray[pointer--] = array[j];
                continue;
            }
            newArray[pointer--] = '0';
            newArray[pointer--] = '2';
            newArray[pointer--] = '%';
        }

        return new String(newArray);
    }
}