foo.cc: In function 'int main()':
foo.cc:11:13: error: 't' was not declared in this scope
         if((t[i]=='+'||t[i]=='-'||t[i]=='*'||t[i]=='/')&&(t[i+1]=='+'||t[i+1]=='-'||t[i+1]=='*'||t[i+1]=='/'))
             ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。