%{
int plus=0,minus=0,mult=0,divi=0;
int opnd=0,op=0;
int n;
%}
%%
[0-9a-zA-Z]+ {opnd++;}
[0-9a-zA-Z]+\+\-\*\/[0-9A-Za-z]+ {n=0;}
[\+]+ {plus++;op++;}
[\-]+ {minus++;op++;}
[\*]+ {mult++;op++;}
[\/]+ {divi++;op++;}
%%
main()
{
printf("enter the expression");
yylex();
printf("\n +::=%d",plus);
printf("\n -::=%d",minus);
printf("\n *::=%d",mult);
printf("\n /::=%d",divi);
printf("\n number of operators =%d",op);
printf("\n number of operands =%d",opnd);
if((n==0)&&(opnd=op+1))
printf("\n valid expresion");
else
printf("\n invalid expression");
}

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MTMrMTIrYSs0LTMvNSoy

13+12+a+4-3/5*2