C++ 为什么指针一片狼藉？我找不出来哪里指针跑飞了

Question

构造两个带有表头结点的有序单链表La、Lb，编写程序实现将Lb融合到La中。 融合的思想是：依次将Lb的每一个结点按数值大小插入到La中。
输入数据为两行有序数据，分别有5个数据。建立两个链表并将每行数据存入链表结点的数据域。
输出为一行10个数据，每个数据之间有一个空格。要求在融合数据后再遍历链表La，输出其数据域的值。

#include <iostream>
#include <cmath>
#include <string>
#include <string.h>
#include <iomanip>
#include <fstream>
using namespace std;

struct node {
    int data;
    node *next;
};

struct list {
    node *head;
    int len;
};

void begin(list &a, int n) {
    node *ptr = new node;
    ptr->data = n;
    ptr->next = NULL;
    if (a.head == NULL) {
        a.head = ptr;
        a.len = 1;
    } else {
        node *pt = a.head;
        while (pt->next != NULL) {
            pt = pt->next;
        }
        pt->next = ptr;
        a.len++;
    }
    delete ptr;
}

void sort(list &a, list &b) {
    node *pt = b.head;
    node *ptr = a.head;
    while (pt) {
            node *ptr = a.head;
            if ((pt->data) < (ptr->data) ) {
            node *temp = pt;
            temp->next = ptr;
            a.head = temp;
            pt = pt->next;
            continue;
        }
        while (pt->data > ptr->data) {
            ptr = ptr->next;
        }
        node *temp = pt;
        temp->next = ptr->next;
        ptr->next = temp;
        pt = pt->next;
    }
}

void show(list &a) {
    node *ptr = new node;
    ptr = a.head;
    for (int j = 0; j < 10; j++) {
        cout << ptr->data << " ";
        ptr = ptr->next;

    }
    delete ptr;
}


int main() {
    int i = 0, n = 0;
    list a, b;
    a.head = NULL;
    a.len = 0;
    for (i = 0; i < 5; i++) {
        cin >> n;
        begin(a, n);
    }
    b.head = NULL;
    b.len = 0;

    for (i = 0; i < 5; i++) {
        int n = 0;
        cin >> n;
        begin(b, n);
    }
    show(a);


    return 0;
}

Answer 1

45和54行，temp->next丢了