C語言連結串列的5種常見操作

• 單鏈表反轉
• 連結串列中環的檢測
• 兩個有序的連結串列合併
• 刪除連結串列倒數第n個結點
• 求連結串列的中間結點

Ref

typedef struct list{
	int item;
	struct list* next;
}myList

單鏈表反轉

myList* invList(myList* head){
	if(head == null) return null;
	
	myList* prev = null, * next = null;
	while
 
(head){
		next = head->next; 
		head->next = prev;	
		prev = head;
		heady = next;
	}
	return head;
}

連結串列中環的檢測

int hasCycle(myList* head){
	myList* fast = head;
	myList* low = head;

	while(fast != NULL && fast->next != NULL){
		low = low->next;
		fast = fast->next->next;
 

		if (low == fast){
			return 1;
		}
	}

	return 0;
}

兩個有序的連結串列合併

myList* mergeList(myList* li1, myList* li2){
	myList head = {0};
	myList* pRes = &head;

	while(1){
		if(li1 == NULL){
			pRes->next = li2;
		}

		if (li2 == NULL){
			pRes->next = li1;
		}

		if(li1->item < li2->
 
item){
			pRes->next = li1;
			li1 = li1->next;
		}else{
			pRes->next = li2;
			li2 = li2->next;
		}
		pRes = pRes->next;
	}

	return head;
}

刪除連結串列倒數第n個結點

myList* removeNthFromEnd(myList* head,int n){
	myList* fast = head;
	myList* prev = NULL;
	myList* next = head;
	int k = n;
	
	/*快指標往後移動k-1*/
	while((k > 1) && (fast != NULL)){
		fast = fast->next;
		k--;
	}
	
	/*說明連結串列數目不足n個*/
	if (fast == NULL){
		return head;
	}
	
	/*快指標移動至最後時，prev到達倒數第n個*/
	while (fast->next != NULL){
		fast = fast->next;
		prev = next;
		next = next->next;
	}

	
	if(prev == NULL){
		//倒數第n個為第一個
		head = head->next;
	}else{
		prev->next = prev->next->next;
	}

	return head;
}

求連結串列的中間結點

myList* middleNode(myList* head)
{
	myList* fast = head;
	myList* low = head;

	while(fast != NULL && fast->next != NULL)
	{
		low = low->next;
		fast = fast->next->next;
	}

	return low;
}