程序员面试金典-面试题 01.06. 字符串压缩

class Solution {
    public String compressString(String S) {
        if(S.length() == 0)
            return S;
        int times = 0;
        StringBuilder str = new StringBuilder();
        char ch = S.charAt(0);
        for(int i = 0; i < S.length(); ++i){
            if(S.charAt(i) == ch){
                times++;
            }else{
                str.append(ch);
                str.append(times);
                times = 1;
                ch = S.charAt(i);
            }
        }
        str.append(ch);
        str.append(times);
        String res = str.toString();
        return res.length() < S.length() ? res : S;
    }
}