#include <iostream> #include <cstdlib> using namespace std; struct ListNode //默认为public { int data; ListNode* next; ListNode(int x, ListNode* nextNode):data(x), next(nextNode){} }; ListNode* mergeData(ListNode* first, ListNode* second) { if(first == nullptr) return second; if(second == nullptr) return first; //合并两个链表,按从小到大的顺序 ListNode* new_head = new (nothrow) ListNode(0, nullptr); //分配失败返回空指针 if(new_head == nullptr) exit(0); ListNode* ptr = new_head; while(first != nullptr && second != nullptr) { if(first->data < second->data) { ptr->next = first; first = first->next; } else { ptr->next = second; second = second->next; } ptr = ptr->next; } //合并剩余部分(对于数组进行归并排序,这部分可通过设置哨兵来省略) if(first != nullptr) ptr->next = first; if(second != nullptr) ptr->next = second; return new_head->next; } //返回为结点指针类型,需要链表头节点 ListNode* mergeSort(ListNode* head) { //递归调用,首先找到分裂点,对于链表可以使用快慢指针方法 if(head == nullptr || head->next == nullptr) return head; ListNode* fast = head->next; ListNode* slow = head; while(fast != nullptr && fast->next != nullptr) { slow = slow->next; fast = fast->next->next; } //此时slow即为中间点,依次对slow之前的元素和之后的元素递归调用归并排序,然后进行合并 ListNode* se = slow->next; slow->next = nullptr; ListNode* first = mergeSort(head); ListNode* second = mergeSort(se); return mergeData(first, second); } void printList(ListNode* head) { if(head == nullptr) return; cout << head->data << " "; printList(head->next); } int main() { ListNode* head = new ListNode(10, new ListNode(9, new ListNode(8, new ListNode(7, new ListNode(6, new ListNode(5, nullptr)))))); printList(head); cout << endl; ListNode* new_head = mergeSort(head); printList(new_head); return 0; }
时间: 2024-10-26 23:51:13