有头节点时 地址为正常值 插入值时不会改变
没有头节点时 指针指向null 地址为00000000
改变指向时地址改变
而且
每次传入函数时都是00000000 而不是改变后的新值
加入引用后 每次传入的为修改后新值
而不是头指针时 初始指向空的next指针
不加引用也会每次改变
本质原因是
地址在传函数时会更新传入的参数地址为初始值
一旦地址在函数中更改
再次传入函数时不会更新为更改的新值
和头节点有无没有关系
不想用引用 又不想有头节点：将地址传回主函数，避免更新为初始值
#include <iostream>
using namespace std;
struct mylianzhan {
int val;
struct mylianzhan* next;
};
struct mylianzhan* initlz() {
struct mylianzhan* mylz = NULL;
//struct mylianzhan* mylz = new struct mylianzhan;
//mylz->val = 5;
//mylz->next = NULL;
return mylz;
}
struct mylianzhan* jinzhan(struct mylianzhan* mylz, int val) {
cout << mylz<< endl;
//cout << mylz->next << endl;
struct mylianzhan* node1 = new struct mylianzhan;
node1->val = val;
node1->next = mylz;
mylz = node1;
//node1->next = mylz->next;
//mylz->next = node1;
//cout << mylz->next << endl;
cout << mylz << endl;
return mylz;
}
void printlz(struct mylianzhan* mylz) {
while (mylz) {
//printf("%d\n", mylz->val);
cout << mylz->val << endl;
mylz = mylz->next;
}
}
int main() {
struct mylianzhan *mylz = initlz();
//struct mylianzhan* node1 = new struct mylianzhan;
//node1->val = 10;
//node1->next = mylz;
//mylz = node1;
//struct mylianzhan* node2 = new struct mylianzhan;
//node2->val = 20;
//node2->next = mylz;
//mylz = node2;
//cout << mylz->next << endl;
mylz=jinzhan(mylz, 30);
mylz=jinzhan(mylz, 30);
mylz=jinzhan(mylz, 30);
printlz(mylz);
}
