题解 | #链表合并#

#include <stdio.h>
#include <stdlib.h>

typedef struct ListNode {
  int val;
  struct ListNode* next;
} ListNode;

ListNode* createList() {
  ListNode* head = NULL, * tail = NULL;
  int val;
  while (scanf("%d", &val) != EOF) {
    ListNode* node = (ListNode*)malloc(sizeof(ListNode));
    node->val = val;
    node->next = NULL;
    if (head == NULL) {
      head = node;
      tail = node;
    } else {
      tail->next = node;
      tail = tail->next;
    }
    if (getchar() == '\n') {
      break;
    }
  }
  return head;
}

ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
  ListNode dummy = {0, NULL};
  ListNode* tail = &dummy;
  while (l1 && l2) {
    if (l1->val < l2->val) {
      tail->next = l1;
      l1 = l1->next;
    } else {
      tail->next = l2;
      l2 = l2->next;
    }
    tail = tail->next;
  }
  tail->next = l1 ? l1 : l2;
  return dummy.next;
}

void printList(ListNode* head) {
  while (head) {
    printf("%d ", head->val);
    head = head->next;
  }
  printf("\n");
}

int main() {
  ListNode* l1 = createList();
  ListNode* l2 = createList();
  ListNode* l3 = mergeTwoLists(l1, l2);
  printList(l3);
  return 0;
}