1.5---字符串压缩（CC150）

import java.util.*;
 
public class Zipper {
    public String zipString(String str) {
        // write code here
       if(str.length() == 0 ) return str;
        int flag = 0;
        int num = 1;
        StringBuffer sb = new StringBuffer();
        char tmp = str.charAt(0);
        for(int i = 1; i < str.length(); i++){
            if(str.charAt(i) == tmp){
                num++;
                flag = 1;
            }
            else{
                sb.append(tmp);
                sb.append(num);
                tmp = str.charAt(i);
                num = 1;
            }
        }
        sb.append(tmp);
        sb.append(num);
        if(flag == 0 || sb.length() >= str.length()) return str;
        else return sb.toString();
    }
}