【剑指offer】替换空格

1. 直接调用函数和new StringBuffer然后append 简直没谁了...

public class Solution {
    public static String replaceSpace(StringBuffer str) {
        if (str == null) {
            return null;
        }

        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == ' ') {
                count++;
            }
        }

        int l = str.length() - 1;
        int r = l + count * 2;
        str.setLength(r + 1);

        while (l >= 0) {
            if (str.charAt(l) != ' ') {
                str.setCharAt(r, str.charAt(l));
                r--;
            } else {
                str.replace(r - 2, r + 1, "%20");
                r -= 3;
            }
            l--;
        }


        return str.toString();
    }
}