动态数组: 开辟销毁内存空间的次数相对比较少, 但可能造成内存空间浪费;
双向链表: 开辟销毁内存空间的次数相对较多, 但不会造成内存空间浪费.
- 链表翻转
面试题24. 反转链表
// O(n)
struct ListNode* reverseList(struct ListNode* head){
if (head == NULL || head->next == NULL) {
return head;
}
struct ListNode *newHead = NULL;
while (head) {
struct ListNode *temp = head->next;
head->next = newHead;
newHead = head;
head = temp;
}
return newHead;
}
// 递归 - O()
struct ListNode* reverseList(struct ListNode* head){
if (head == NULL || head->next == NULL) {
return head;
}
struct ListNode *newHead = reverseList(head->next);
head->next->next = head;
head->next = NULL;
return newHead;
}
- 快慢指针
141. 环形链表
bool hasCycle(struct ListNode *head) {
if (head == NULL || head->next == NULL) {
return false;
}
struct ListNode *slow = head;
struct ListNode *fast = head->next;
while (fast && fast->next) {
if (slow == fast) {
return true;
}
slow = slow->next;
fast = fast->next->next;
}
return false;
}
void deleteNode(struct ListNode* node) {
node->val = node->next->val;
node->next = node->next->next;
}
// 哨兵节点法
struct ListNode* removeElements(struct ListNode* head, int val){
struct ListNode *sentinelNode = malloc(sizeof(struct ListNode));
sentinelNode->next = head;
struct ListNode *curr = head;
struct ListNode *prev = sentinelNode;
while (curr) {
if (curr->val == val) {
prev->next = curr->next;
} else {
prev = curr;
}
curr = curr->next;
}
return sentinelNode->next;
}
struct ListNode * deleteDuplicates(struct ListNode* head) {
struct ListNode *sential = malloc(sizeof(struct ListNode));
sential->next = head;
struct ListNode *pre = sential;
struct ListNode *curr = head;
while (curr && curr->next) {
if (curr->val == curr->next->val) {
pre->next = curr->next;
} else {
pre = curr;
}
curr = curr->next;
}
return sential->next;
}
栈(stack)
LIFO(last in first out)
push pop
队列(queue)
FIFO - 基于双向列表实现
