/in/foo.cc: In function 'int main()':
/in/foo.cc:12:13: warning: array subscript has type 'char' [-Wchar-subscripts]
   if(ch[a[i]]==0){
             ^
/in/foo.cc:13:11: warning: array subscript has type 'char' [-Wchar-subscripts]
    ch[a[i]]=b[i];
           ^
/in/foo.cc:16:14: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(ch[a[i]]!=b[i]){
              ^
/in/foo.cc:28:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<c.length();i++){
              ~^~~~~~~~~~~
/in/foo.cc:29:16: warning: array subscript has type 'char' [-Wchar-subscripts]
   cout<<ch[c[i]];
                ^