palindrome_linked_list
palindrome_linked_list.cpp 源码
// 回文链表
#include "vector"
using namespace std;
struct ListNode {
int val;
ListNode *next;
ListNode() : val(0), next(nullptr) {}
ListNode(int x) : val(x), next(nullptr) {}
ListNode(int x, ListNode *next) : val(x), next(next) {}
};
class Solution {
public:
// 放入数组再比较
bool isPalindrome1(ListNode* head) {
vector<int> arr;
while (head) {
arr.push_back(head->val);
head = head->next;
}
for (int i = 0, j = arr.size() - 1; i < j; i++, j--) {
if (arr[i] != arr[j]) {
return false;
}
}
return true;
}
// 找到中间节点再反转再比较
bool isPalindrome2(ListNode* head) {
// 找到中间节点
ListNode* slow = head, *fast = head;
while (fast && fast->next) {
slow = slow->next;
fast = fast->next->next;
}
// 反转
ListNode* prev = nullptr, *p = head;
while (p != slow) {
ListNode* next = p->next;
p->next = prev;
prev = p;
p = next;
}
ListNode* q = slow;
if (fast != nullptr) {
q = slow->next;
}
while (prev && q) {
if (prev->val != q->val) {
return false;
}
prev = prev->next;
q = q->next;
}
return true;
}
};
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