多项式相加

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

struct Node{
	int coef;
	int expn;
	Node *next;
};

Node n1[1000],n2[1000];
Node *insertNode(Node *head,int coef,int expn){
	Node *newnode = new Node;
	newnode->coef = coef;
	newnode->expn = expn;
	newnode->next = NULL;
	if(head->next == NULL)
		head->next = newnode;
	else{ 
		Node *p = head->next;
		Node *pre = head;
		while(p){
			if(p->expn > newnode->expn){
				p = p->next;
				pre = pre->next;
			}else{
				pre->next = newnode;
				newnode->next = p;
			}    
		}
		if(p == NULL)
			pre->next = newnode;
	}
	return head;
}

Node *addNode(Node *head1,Node *head2){
	Node *p1 = head1->next;
	Node *pre = head1;
	Node *p2 = head2->next;
	while(p1 && p2){
		if(p1 ->expn == p2->expn){
			p1->coef += p2->coef;
			if(p1->coef == 0)
				pre->next = p1->next;
			else
			{
				p1 = p1->next;
				pre = pre->next;
			}
			p2 = p2->next;
		}
		else if(p1 ->expn > p2->expn){
			p1 = p1->next;
			pre = pre->next;
		}
		else{
			Node *p = p2;
			p2 = p2->next;
			pre->next = p;
			p->next = p1;
			pre = p;
		}
	}
	if(p2)
		pre->next = p2;
	return head1;
}
int main()
{ 
	int n,m;
	while(cin >> n){
		Node *head1 = new Node;
		Node *head2 = new Node;
		head1->next = NULL;
		head2->next = NULL;
		for(int i = 0; i < n; i++){
			int coef,expn;
			cin >> coef >> expn;
			head1 = insertNode(head1,coef,expn);
		}
		cin >> m;
		for(int i = 0; i < m; i++){
			int coef,expn;
			cin >> coef >> expn;
			head2 = insertNode(head2,coef,expn);
		}
		head1 = addNode(head1,head2);
		Node *p = head1->next;
		while(p && p->next){
			cout << p->coef << " " << p->expn << " ";
			p = p->next;
		}
		if(p)
			cout << p->coef << " " << p->expn << endl;
	}
	return 0;
}