rt 代码1

ll x=-2140000000;
		if(a1.size())x=max(x,a1.front());
		if(a2.size())x=max(x,a2.front());
		if(a3.size())x=max(x,a3.front());
		if(x==a1.front())a1.pop();
		else if(x==a2.front())a2.pop();
		else a3.pop();

代码2

ll x=-2140000000;
if(a1.size()&& x<a1.front())w=1,x=a1.front();
		if(a2.size()&&x<a2.front())x=a2.front(),w=2;
		if(a3.size()&&x<a3.front())x=a3.front(),w=3;
		if(w==1)a1.pop();
		else if(w==2)a2.pop();
		else a3.pop();

求为什么代码一会出错，循环一完三个队列里全是0