列表的插入与删除：
定义一个列表（List）模板类，实现列表的初始化、插入、删除操作：
1 template <typename T> 2 struct ListNode //listnode模板类 3 { 4 T data; //数值 5 ListNode<T> * pred; //前驱 引用 6 ListNode<T> * succ; //后继 引用 7 }; 8 9 template <typename T> 10 class List 11 { 12 private: 13 int size; //规模 14 ListNode<T> *header; //头哨兵 15 ListNode<T> *trailer; //尾哨兵 16 public: 17 List(); 18 ListNode<T> * insertAsFirst(T e); //e当做首节点插入 19 ListNode<T> * insertAsLast(T e); //e当做末节点插入 20 ListNode<T> * insertAsPred(ListNode<T> *p, T e); //e当做节点的前驱插入 21 ListNode<T> * insertAsSucc(ListNode<T> *p, T e); //e当做节点的后继插入 22 T remove(ListNode<T> *p); 23 T find(T e, int n, T p); 24 T & operator[] (int r); 25 int getsize(); 26 }; 27 28 template <typename T> 29 List<T>::List() 30 { 31 header = new ListNode<T>; //分配节点 32 trailer = new ListNode<T>; //创建头哨兵 尾哨兵 33 header->pred = NULL; header->succ = trailer; //前驱和后继的引用分别指向对方，实现互联 34 trailer->pred = header; trailer->succ = NULL; 35 size = 0; 36 } 37 38 template <typename T> 39 ListNode<T> * List<T>::insertAsFirst(T e) //e当做首节点插入 40 { 41 ListNode<T> * x = new ListNode<T>; 42 ListNode<T> * p = header->succ; 43 44 x->data = e; 45 x->pred = header; 46 x->succ = p; 47 header->succ = x; 48 p->pred = x; 49 size++; 50 return x; 51 } 52 53 template <typename T> 54 ListNode<T> * List<T>::insertAsLast(T e) //e当做末节点插入 55 { 56 ListNode<T> * x = new ListNode<T>; 57 ListNode<T> * p = trailer->pred; 58 59 x->data = e; 60 x->pred = p; 61 x->succ = trailer; 62 p->succ = x; 63 trailer->pred = x; 64 size++; 65 return x; 66 } 67 68 template <typename T> 69 ListNode<T> * List<T>::insertAsPred(ListNode<T> *p, T e) //e当做节点的前驱插入 70 { 71 ListNode<T> * x = new ListNode<T>; 72 ListNode<T> * q = p->pred; 73 74 x->data = e; 75 x->pre = q; 76 x->succ = p; 77 q->succ = x; 78 p->pred = x; 79 size++; 80 return x; 81 } 82 83 template <typename T> 84 ListNode<T> * List<T>::insertAsSucc(ListNode<T> *p, T e) //e当做节点的后继插入 85 { 86 ListNode<T> * x = new ListNode<T>; 87 ListNode<T> * q = p->succ; 88 89 x->data = e; 90 x->pre = p; 91 x->succ = q; 92 q->pred = x; 93 p->succ = x; 94 size++; 95 return x; 96 } 97 98 template <typename T> 99 T List<T>::remove(ListNode<T> *p) 100 { 101 T e; 102 ListNode<T> * m = p->pred; 103 ListNode<T> * n = p->succ; 104 e = p->data; 105 m->succ = n; 106 n->pred = m; 107 108 delete p; 109 size--; 110 return e; 111 } 112 113 template <typename T> 114 T List<T>::find(T e, int n, T p) 115 { 116 while (0 < n--) 117 if (e == (p = p->pred)->data) return p; 118 return NULL; 119 } 120 121 template <typename T> 122 T & List<T>::operator[] (int r) 123 { 124 ListNode<T> * p = header->succ; 125 while(r>0) 126 { 127 p = p->succ; 128 r--; 129 } 130 return p->data; 131 } 132 133 template <typename T> 134 int List<T>::getsize() 135 { 136 return size; 137 }
