题目
书店店员有一张链表形式的书单，每个节点代表一本书，节点中的值表示书的编号。为更方便整理书架，店员需要将书单倒过来排列，就可以从最后一本书开始整理，逐一将书放回到书架上。请倒序返回这个书单链表。
输入
head = [3,6,4,1]
输出
[1,4,6,3]
解法 1：递归
class Solution {
public:std::vector<int> reverseBookList(ListNode* head) {recur(head);return res;}
private:std::vector<int> res;void recur(ListNode* head) {if (head == nullptr) return;recur(head->next);res.push_back(head->val);}
};
解法 2：辅助栈法
class Solution {
public:std::vector<int> getResultList(ListNode* head) {std::stack<int> stk;std::vector<int> res;while(head!=nullptr) {stk.push(head->val);head = head->next;}while(!stk.empty()) {res.push_back(stk.top());stk.pop();}return res;}
};
完整代码
#include <iostream>
#include <vector>
struct ListNode {int val;ListNode* next;ListNode(int x) : val(x), next(NULL) {}
};class Solution {
public:std::vector<int> reverseBookList(ListNode* head) {recur(head);return res;}
private:std::vector<int> res;void recur(ListNode* head) {if (head == nullptr) return;recur(head->next);res.push_back(head->val);}
};void test() {ListNode* head = new ListNode(1);ListNode* n2 = new ListNode(2);ListNode* n3 = new ListNode(3);ListNode* n4 = new ListNode(4);ListNode* n5 = new ListNode(5);head->next = n2;n2->next = n3;n3->next = n4;n4->next = n5;Solution solution;std::vector<int> reversedList = solution.reverseBookList(head);std::cout << "Result: " << std::endl;for (int num : reversedList) {std::cout << num << " ";}std::cout << std::endl;}int main() {test();return 0;
}
#include <iostream>
#include <vector>
#include <stack>
struct ListNode {int val;ListNode* next;ListNode(int x) : val(x), next(NULL) {}
};class Solution {
public:std::vector<int> getResultList(ListNode* head) {std::stack<int> stk;std::vector<int> res;while(head!=nullptr) {stk.push(head->val);head = head->next;}while(!stk.empty()) {res.push_back(stk.top());stk.pop();}return res;}
};void test() {ListNode* head = new ListNode(1);ListNode* n2 = new ListNode(2);ListNode* n3 = new ListNode(3);ListNode* n4 = new ListNode(4);ListNode* n5 = new ListNode(5);head->next = n2;n2->next = n3;n3->next = n4;n4->next = n5; Solution solution;std::vector<int> testList = solution.getResultList(head);std::cout << "Result: " << std::endl;for (int x : testList) {std::cout << x << " ";}std::cout << std::endl;
}
int main() {test();return 0;
}
