简单链表

C++单链表基本操作（代码） #include <iostream> #include <stdlib.h> #include <assert.h> using namespace std;  // list node structure typedef struct _NODE{       int data;       struct _NODE *next; }NODE, *PNODE;  // create a list, return the pointer to the head node PNODE create() {       PNODE head = NULL;       PNODE current = NULL;       PNODE temp = NULL;       int data = 0;       int cnt = 1;        temp = new NODE;       assert(temp != NULL);       cout << "Please input numbers, end with 0" << endl;       cin >> data;       temp->data = data;        while(temp->data != 0)       {             if(cnt == 1)             {                   // head node                   current = temp;                   head = current;             }else{                   current->next = temp;             }              current = temp;             temp = new NODE;             assert(temp != NULL);       }        current->next = NULL; // last node       return head; }  // print data of each node in the list, from head to tail void print(PNODE list) {       if(!list) { cout << "empty list" << endl; return; }        PNODE current = list;       while(current)       {             cout << current->data << " ";             current = current->next;       }       cout << endl; }  // free each node in the list void destroy(PNODE &list) // pointer reference {       if(!list) { cout << "destroy ok" << endl; return; }        PNODE current = list;       PNODE temp = NULL;       while(current)       {             cout << "destroy " << current->data << endl;             temp = current->next;             delete current;             current = temp;       }       list = current;       cout << "destroy ok" << endl; }  // count the nodes in the list int count(PNODE list) {       if(!list) return 0;              int cnt = 0;       // traverse the list       PNODE current = list;       while(current)       {             ++cnt;             current = current->next;       }        return cnt; }  // find value in the list, return the position of the node(start from 1...) int find(PNODE list, int data) {       if(!list) { cout << "value " << data << " not found in empty list" << endl; return 0; }        int cnt = 0;       PNODE current = list;       // traverse the list       while(current)       {             ++cnt;             if(current->data == data)             {                   // found                   cout << "find value " << data << " in node " << cnt << endl;                   return cnt;             }              current = current->next;       }        // not found       cout << "value " << data << " not found" << endl;       return 0; }  // reverse the list(loop) void reverse_loop(PNODE &list) {       if(!list) return;        PNODE previous = NULL;       PNODE current = NULL;       PNODE next = NULL;        previous = list;       current = previous->next;       while(current)       {             next = current->next;             current->next = previous;             previous = current;             current = next;       }       // change head to tail       list->next = NULL;       list = previous;       // cout << "reverse ok" << endl; }  // reverse the list(recursive) PNODE reverse_rec(PNODE list) {       if(!list) return NULL;        PNODE tail = reverse_rec(list->next);       if(!tail) return list; // find the last node of list        // assume the rest of the list is reversed, we only need to reverse the first two nodes       list->next->next = list; // the second node pointer to the first node       list->next = NULL; // the first node pointer to NULL(new tail)        return tail; // unchanged(new head) }  // insert node in list void insert(PNODE &list, int data) {       PNODE node = new NODE;       assert(node != NULL);       node->data = data;              // test       cout << "insert value " << data << endl;        if(!list)        {             node->next = NULL;              list = node;              return ;       }        PNODE current = list;       while(current->data < node->data && current->next)       {             // find the right position             current = current->next;       }        if(current == list)       {             // insert before the first node             node->next = current;             list = node;             return ;       }              node->next = current->next;       current->next = node;        return ; }  // delete specified node(start from 0) void remove(PNODE &list, int pos) {       if(!list) return ;        PNODE current = list;       if(pos == 0)       {             // remove first node             list = current->next;             cout << "delete first node " << current->data << endl;             delete current;             return ;       }        // find pos in list       int cnt = 0;       PNODE temp = NULL;       while(current->next)       {             if(++cnt == pos)             {                   // found                   temp = current->next;                   current->next = temp->next;                   cout << "delete node " << pos+1 << " with value " << temp->data << endl;                   delete temp;                   return ;             }              current = current->next;       }        // not found       cout << "node " << pos+1 << " not found in list" << endl;       return ; }  // find the middle node of list(rounded-up) PNODE middle(PNODE list) {       if(!list) return NULL;        PNODE first = NULL;       PNODE second = NULL;       first = second = list;       int pos = 1;              while(second->next && second->next->next)       {             first = first->next; // step one by one             second = second->next->next; // step two each time             pos++;       }        cout<< "find middle node " << pos << "(" << count(list) << ") with value " << first->data << endl;       return first; }  // exchange two integers void exchange(int &i, int &j) {       i ^= j;       j ^= i;       i ^= j; }  // sort order(little -> big) void sort(PNODE &list) {       if(list == NULL || list->next == NULL) return ;        int temp = 0;       PNODE current = list;       int cnt = count(list);       for(int i = 1; i < cnt; i++)       {             current = list;             for(int j = 0; j < cnt - i; j++)             {                   if(current->data > current->next->data)                   {                         exchange(current->data, current->next->data);                   }                   current = current->next;             }       } }  // merge two sorted lists into one list PNODE merge_loop(PNODE list1, PNODE list2) {       if(!list1) return list2;       else if(!list2) return list1;        PNODE new_list = NULL;       if(list1->data <= list2->data)       {             new_list = list1;             list1 = list1->next;       }else{             new_list = list2;             list2 = list2->next;       }        PNODE current = new_list;       while(list1 && list2)       {             if(list1->data <= list2->data)             {                   current->next = list1;                   list1 = list1->next;                   current = current->next;             }else{                   current->next = list2;                   list2 = list2->next;                   current = current->next;             }       }        if(!list1) current->next = list2;       if(!list2) current->next = list1;        return new_list; }  // merge two sorted lists into one list PNODE merge_rec(PNODE list1, PNODE list2) {       if(!list1) return list2;       else if(!list2) return list2;        PNODE mlist = NULL;       if(list1->data <= list2->data)       {             mlist = list1;             mlist->next = merge_rec(list1->next, list2);       }else{             mlist = list2;             mlist->next = merge_rec(list1, list2->next);       }        return mlist; }  // start from here int main() {       // create       PNODE slist = create();       PNODE slist2 = create();       cout << "after input: " << endl;       print(slist);       print(slist2);        // sort       cout << "after sorted: " << endl;       sort(slist);       sort(slist2);       print(slist);       print(slist2);        // merge       cout << "after merged: " << endl;       // PNODE mlist = merge_loop(slist, slist2);       PNODE mlist = merge_rec(slist, slist2);       print(mlist);        // find       cout << "nodes of mlist: " << count(mlist) << endl;       find(mlist, 0);       find(mlist, 8);       find(mlist, 20);        // insert       insert(mlist, 0);       insert(mlist, 8);       insert(mlist, 10);       print(mlist);        // middle       middle(mlist);        // remove       remove(mlist, 0);       remove(mlist, 8);       remove(mlist, 10);       print(mlist);        // middle       middle(mlist);        // reverse       reverse_loop(mlist);       // mlist = reverse_rec(mlist);       cout << "after reversed: " << endl;       print(mlist);        // destroy       destroy(mlist);        system("PAUSE");       return 0; }