单链表逆序或者逆序输出
分为两种情况，一种是只逆序输出，实际上不逆序；另一种是把链表逆序。
********************逆序输出***********************
1 #include<iostream> 2 #include<stack> 3 #include<assert.h> 4 using namespace std; 5 6 7 typedef struct node{ 8 int data; 9 node * next; 10 }node; 11 12 //尾部添加 13 node * add(int n, node * head){ 14 node * t = new node; 15 t->data = n; 16 t->next = NULL; 17 if (head == NULL){ 18 head = t; 19 } 20 else if (head->next == NULL){ 21 head->next = t; 22 } 23 else{ 24 node * p = head->next; 25 while (p->next != NULL){ 26 p = p->next; 27 } 28 p->next = t; 29 } 30 return head; 31 } 32 33 //顺序输出 34 void print(node * head){ 35 node * p = head; 36 while (p != NULL){ 37 cout << p->data << " "; 38 p = p->next; 39 } 40 cout << endl; 41 } 42 43 //递归 44 void reversePrint(node * p){ 45 if (p != NULL){ 46 reversePrint(p->next); 47 cout << p->data << " "; 48 } 49 } 50 51 //栈 52 void reversePrint2(node * head){ 53 stack<int> s; 54 while (head != NULL){ 55 s.push(head->data); 56 head = head->next; 57 } 58 59 while (!s.empty()){ 60 cout << s.top() << " "; 61 s.pop(); 62 } 63 } 64 65 int main(){ 66 67 node * head = NULL; 68 for (int i = 1; i <= 5; i++){ 69 head = add(i, head); 70 } 71 print(head); 72 reversePrint(head); 73 reversePrint2(head); 74 system("pause"); 75 return 0; 76 }
逆序输出可以用三种方法: 递归，栈，逆序后输出。最后一种接下来讲到。
*********************单链表逆序********************
1 #include<iostream> 2 #include<stack> 3 #include<assert.h> 4 using namespace std; 5 6 7 typedef struct node{ 8 int data; 9 node * next; 10 }node; 11 12 node * add(int n, node * head){ 13 node * t = new node; 14 t->data = n; 15 t->next = NULL; 16 if (head == NULL){ 17 head = t; 18 } 19 else if (head->next == NULL){ 20 head->next = t; 21 } 22 else{ 23 node * p = head->next; 24 while (p->next != NULL){ 25 p = p->next; 26 } 27 p->next = t; 28 } 29 return head; 30 } 31 32 //循环 33 node * reverse(node * head){ 34 35 if (head == NULL || head->next == NULL){ 36 return head; 37 } 38 39 node * p1 = head; 40 node * p2 = head->next; 41 node * p3 = NULL; 42 head->next = NULL; 43 44 while (p2 != NULL){ 45 p3 = p2; 46 p2 = p2->next; 47 p3->next = p1; 48 p1 = p3; 49 } 50 head = p1; 51 return head; 52 } 53 54 void print(node * head){ 55 node * p = head; 56 while (p != NULL){ 57 cout << p->data << " "; 58 p = p->next; 59 } 60 cout << endl; 61 } 62 63 64 //递归 65 node * reverse2(node * p){ 66 if (p == NULL || p->next == NULL){ 67 return p; 68 } 69 70 node * newHead = reverse2(p->next); 71 p->next->next = p; 72 p->next = NULL; 73 return newHead; 74 } 75 76 77 int main(){ 78 79 node * head = NULL; 80 for (int i = 1; i <= 5; i++){ 81 head = add(i, head); 82 } 83 print(head); 84 head = reverse(head); 85 print(head); 86 head = reverse2(head); 87 print(head); 88 89 system("pause"); 90 return 0; 91 }
这里链表逆序用了两种方法：循环，递归。理解的方法是在纸上自己画一下。
