Expand "2[ab3[c]]" into "abcccabccc"

eexp.c

char*f(char*s){char*t;int n;for(t=s;*t;t++)if(*t==']')break;
else if(*t>>4==3){for(n=*(s=t++)-48;*t>>4==3;n=n*10+(*t++-48));
if(*t=='[')for(s=t+1;n--;t=f(s));else for(t--;s<=t;putchar(*s++));}
else putchar(*t);return t;}int main(int c,char**v){f(v[1]);}