回文判断C++

#include
#include
using namespace std;
int main(){
string a;
int len,q,p=0,flag=0;//标志位

cout<<"请输入字符串"<<endl; 
cin>>a;
q=a.length()-1;
while(p<q){
	if(a[p]!=a[q]){
		flag++;
	}
	p++;
	q--;
}

if(flag!=0){
	cout<<"不是回文"<<endl;
}else{
	cout<<"是回文"<<endl; 
}

return 0;

}