C# (Visual C# Interactive Compiler), 134 bytes
s=>{var t="";for(;t=="";){for(int i=0,l=s.Length;i<l;i++)t+=i==l-1||s[i]!=s[i+1]?s[i]+"":s[i++]*2-96+"";if(s!=t){s=t;t="";}}return t;}
dana
- 2.7k
- 1
- 15
- 11