题解 | 链表内指定区间反转

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @param m int整型 
 * @param n int整型 
 * @return ListNode类
 */
struct ListNode* reverseBetween(struct ListNode* head, int m, int n ) {
    // write code here b
    if(head == NULL || head ->next ==NULL){
        return head;
    }
    struct ListNode* dummy = (struct ListNode*)malloc(sizeof(struct ListNode));
    dummy->next = head;
    struct ListNode* prev = dummy;
    for(int i = 1;i<m;i++){
        prev = prev -> next;
    }
    struct ListNode* curr = prev->next;
    for(int i = 0;i<n-m;i++){
        struct ListNode *next = curr->next;
        curr ->next = next->next;
        next->next = prev ->next;
        prev ->next = next;
    }
    struct ListNode *newHead = dummy ->next;
    free(dummy);
    return newHead;
}