c - leetcode#24 Swap Nodes in Pairs 运行时错误(C语言)

Question

我尝试在 this link 上回答问题.
但是，我发现我的答案在少量输入上效果很好，但是 leetcode 网站在输入上给出了运行时错误

[4,77,57,79,24,47,21,42,38,54,26,28,30,85,32,40,62,28,89,37,24,3,51,72,59,49,7,60,44,7,27,48,37,37,27,13,36,49,55,26,55,33,55,85,19,39,25,33,68,14,70,44,70,73,68,29,22,27,89,66,35,69,67,24,58,94,37,46]

这是我的代码，有人能告诉我发生了什么吗？

    /**
     * Definition for singly-linked list.
     * struct ListNode {
     *     int val;
     *     struct ListNode *next;
     * };
     */
    struct ListNode* swapPairs(struct ListNode* head)
    {
        struct ListNode *dummy, *pi, *pj, *end;
        dummy->next = head;
        end = dummy;
        while(true){
            pi = end->next;    
            if(pi == NULL){
                break;
            }else{ 
                pj = pi->next;
            }
            if(pj == NULL){
                break;
            }
            end->next = pi->next;
            pi->next = pj->next;
            pj->next = pi;
            end = pi;
        }
        return dummy->next;
    }

Answer 1

struct ListNode *dummy, *pi, *pj, *end;
dummy->next = head;

你没有初始化dummy ptr，但是你使用了它。