//链表算法:
//题目:
//给定一个链表,删除链表的倒数第 n 个节点,并且返回链表的头结点。
//
//问题函数定义:
//
//cpp
//ListNode* removeNthFromEnd(ListNode* head, int n);
//裁判测试程序样例:
//
//cpp
#include <iostream>
using namespace std;
struct ListNode {
int val;
ListNode* next;
ListNode(int x) : val(x), next(NULL) {}
};
ListNode* removeNthFromEnd(ListNode* head, int n) {
ListNode* dummy = new ListNode(0); // 使用哑节点简化边界情况处理
dummy->next = head;
ListNode* low = dummy;
ListNode* fast = dummy;
// fast指针先走 n+1 步
for (int i = 0; i < n + 1; ++i) {
if (!fast) return head; // 处理链表长度小于 n 的情况
fast = fast->next;
}
// 同时移动 low 和 fast 指针,直到 fast 到达链表尾部
while (fast) {
low = low->next;
fast = fast->next;
}
// 删除倒数第 n 个节点
ListNode* temp = low->next;
low->next = low->next->next;
delete temp;
ListNode* result = dummy->next;
delete dummy;
return result;
}
void printList(ListNode* head) {
ListNode* curr = head;
while (curr != NULL) {
cout << curr->val << " ";
curr = curr->next;
}
cout << endl;
}
int main() {
ListNode* head = new ListNode(1);
head->next = new ListNode(2);
head->next->next = new ListNode(3);
head->next->next->next = new ListNode(4);
head->next->next->next->next = new ListNode(5);
int n = 2;
cout << "Original list: ";
printList(head);
ListNode* new_head = removeNthFromEnd(head, n);
cout << "List after removing " << n << "th node from end: ";
printList(new_head);
return 0;
}
//输入样例:
//
//链表:1 -> 2 -> 3 -> 4 -> 5
//n = 2
//输出样例:
//
//删除倒数第2个节点后的链表:1 -> 2 -> 3 -> 5