传值操作
#include <iostream> using namespace std; struct ListNode { int m_nValue; ListNode* m_pNext; }; void createList(ListNode *head) { head = new(ListNode); head->m_nValue = 1; head->m_pNext = NULL; } void deleteList(ListNode *p) { ListNode *next = NULL; while(p != NULL) { cout << p->m_nValue << endl; next = p->m_pNext; delete p; p = NULL; p = next; } } int main() { ListNode *head = NULL; createList(head); cout << head << endl; deleteList(head); }
结果
0
分析
主函数中的指针head为传值调用，传到函数并没有改变主函数中的值，图示
改进的措施就是引用传值，直接操纵原指针。
改进1
#include <iostream> using namespace std; struct ListNode { int m_nValue; ListNode* m_pNext; }; void createList(ListNode *&head) { head = new(ListNode); head->m_nValue = 1; head->m_pNext = NULL; } void deleteList(ListNode *p) { ListNode *next = NULL; while(p != NULL) { cout << p->m_nValue << endl; next = p->m_pNext; delete p; p = NULL; p = next; } } int main() { ListNode *head = NULL; createList(head); cout << head << endl; deleteList(head); }
改进2
#include <iostream> using namespace std; struct ListNode { int m_nValue; ListNode* m_pNext; }; void createList(ListNode **head) { *head = new(ListNode); (*head)->m_nValue = 1; (*head)->m_pNext = NULL; } void deleteList(ListNode *p) { ListNode *next = NULL; while(p != NULL) { cout << p->m_nValue << endl; next = p->m_pNext; delete p; p = NULL; p = next; } } int main() { ListNode *head = NULL; createList(&head); cout << head << endl; deleteList(head); }
细节：->优先级高于*
原文：http://www.cnblogs.com/kaituorensheng/p/3603611.html