數據結構-將兩個有序鏈表head1 head2,合併爲一個鏈表

堅持每月一篇

 

list的構造就不重複了，詳見鏈表的構造

 

 

//遞歸方式
PNode Merge(PNode head1, PNode head2)
{
	PNode newhead = NULL;
	if(NULL == head1) {
		return head2;
	}
	else if (NULL == head2) {
		return head1;
	}
	if(head1->data <= head2->data) {
		newhead = head1;
		newhead->next = Merge(head1->next, head2);
	}
	else {
		newhead = head2;
		newhead->next = Merge(head1, head2->next);
	}
	return newhead;
}

//非遞歸方式
PNode Merge2(PNode head1, PNode head2)
{
	PNode head = NULL;
	//先找到兩個表中較小的頭結點爲新的頭結點
	if (head1->data <= head2->data){
		head = head1;
		head1 = head1->next;
	}
	else {
		head = head2;
		head2 = head2->next;
	}
	//需要記錄一下頭結點的位置，不能用head直接操作，否則會丟失這個新鏈表
	PNode cur = head;
	while (NULL != head1 && NULL != head2) {
		if(head1->data <= head2->data) {
			cur->next = head1;
			cur = head1;
			head1 = head1->next;
		}
		else {
			cur->next = head2;
			cur = head2;
			head2 = head2->next;
		}
	}
	// 走到這裏的條件是兩個鏈表中一定有一個遍歷完
	// 如果剩下的鏈表還沒遍歷完，則把鏈表接到後面
	if (NULL != head1) {
		cur->next = head1;
	}
	if (NULL != head2) {
		cur->next = head2;
	}
	return head;
}

main.c

 

 

	PNode head1 = initList();
	PNode head2 = initList();
	PNode node1 = makenode(1);
	PNode node2 = makenode(3);
	PNode node3 = makenode(5);
	PNode node4 = makenode(2);
	PNode node5 = makenode(4);
	PNode node6 = makenode(6);
	insert(head1,head1,node1);
	insert(head1,node1,node2);
	insert(head1,node2,node3);
	insert(head2,head2,node4);
	insert(head2,node4,node5);
	insert(head2,node5,node6);
	PNode newhead = Merge(head1, head2);
	while(NULL != newhead) {
		printf("newhead data is %d\n", newhead->data);
		newhead = newhead->next;
	}

運行結果

 

 

newhead data is 0
newhead data is 0
newhead data is 1
newhead data is 2
newhead data is 3
newhead data is 4
newhead data is 5
newhead data is 6