两个非降序链表的并集

/*copyright@nciaebupt 转载请注明出处题目：两个非降序链表的并集，1->2->3 和  2->3->5 并为  1->2->3->5 另外只能输出结果，不能修改两个链表的数据。*/#include <cstdlib>#include <iostream>struct List{  int value;  List * next;};List * createList(int * arr, int len){  List * head = NULL;  for(int i = 0; i < len;++i){    List * newnode = new List();    if(head == NULL){      newnode->value= arr[i];      newnode->next = NULL;      head = newnode;    }    else{      newnode->value= arr[i];      newnode->next = head;      head = newnode;    }  }  return head;}void listMerge(List * head1, List * head2){  if(head1 == NULL && head2 == NULL)  return;  if(head1 == NULL){    List * cur = head2;    while(cur != NULL){      std::cout<<cur->value<<" ";      cur = cur->next;    }    std::cout<<std::endl;    return;  }  if(head2 == NULL){    List * cur = head1;    while(cur != NULL){      std::cout<<cur->value<<" ";      cur = cur->next;    }    std::cout<<std::endl;    return;  }  List * cur1 = head1;  List * cur2 = head2;  while(cur1 != NULL && cur2 != NULL){    if(cur1->value < cur2->value){      std::cout<<cur1->value<<" ";      cur1 = cur1->next;    }    else if(cur1->value > cur2->value){      std::cout<<cur2->value<<" ";      cur2 = cur2->next;    }    else{      std::cout<<cur1->value<<" ";      cur1 = cur1->next;      cur2 = cur2->next;    }  }  while(cur1 != NULL){    std::cout<<cur1->value<<" ";    cur1 = cur1->next;  }  while(cur2 != NULL){    std::cout<<cur2->value<<" ";    cur2 = cur2->next;  }  std::cout<<std::endl;}int main(int argc, char ** argv){  int arr1[] = {3,2,1};  int len1 = sizeof(arr1)/sizeof(int);  int arr2[] = {5,3,2};  int len2 = sizeof(arr2)/sizeof(int);  List * head1 = createList(arr1,len1);  List * head2 = createList(arr2,len2);  listMerge(head1,head2);  system("pause");  return 0;}