classSolution{public String compressString(String S){int len = S.length();if(len ==0|| len ==1)return S;
S +=" ";
StringBuilder sb =newStringBuilder();int c =1;for(int i =0; i < len; i++){if(S.charAt(i)!= S.charAt(i +1)){
sb.append(S.charAt(i)).append(c);
c =1;}else{
c++;}if(sb.length()>= len)return S.substring(0, len);}return sb.toString();}}