C++写的链表，一打开程序就直接结束

Question

#include<iostream>
#include<cstdio>
#include<stdlib.h>
using namespace std;
struct ChainChart{
    int key;
    ChainChart *next;
    ChainChart *prev;
};
ChainChart *head,*tail;
void insert(int val){
    ChainChart *add;
    add->next=head->next;
    head->next->prev=add;
    head->next=add;
    add->prev=head;
    add->key=val;
}
ChainChart *Search(int val){
    ChainChart *sea=head->next;
    while(sea!=head&&sea->key!=val){
        sea=sea->next;
    }
    return sea;
}
void deleteChainChart(ChainChart *det){
    if(det==head) return;
    det->prev->next=det->next;
    det->next->prev=det->prev;
    free(det);
}
void print(){
    ChainChart *s=head->next;
    while(s!=head){
        cout<<s->key<<" ";
        s=s->next;
    }
    cout<<"\n";
}
int main(){
    head->next=tail;
    head->prev=head;
    tail->prev=head;
    tail->next=tail;
    int n,num;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>num;
        insert(num);
    }
    print();
}

各位知道是怎么回事吗？刚一打开，就直接结束，根本不执行。

Answer 1

head只是个指针，还没有分配空间呢，你就开始搞next,prev，不死才怪啊
head = (struct ChainChart*)malloc(sizeof(struct ChainChart));
tail = (struct ChainChart*)malloc(sizeof(struct ChainChart));
head->next = ...