92. Reverse Linked List II (List)

class Solution {
public:
    ListNode *reverseBetween(ListNode *head, int m, int n) {

        if(!head || m==n ) return head;
        ListNode * lastOfPrePart = head;
        ListNode * preReverseNode;
        ListNode * firstPostPart;
        ListNode * nextReverseNode;
        ListNode * currentReverseNode;
        
        if(m>1)
        {
            for(int i = 0; i < m-2; i++)
            {
                lastOfPrePart = lastOfPrePart->next;
            }
            currentReverseNode = lastOfPrePart->next;
        }
        else
        {
            currentReverseNode = head;
        }        
        
        nextReverseNode = currentReverseNode->next;
        firstPostPart = currentReverseNode;
        for(int i = m; i < n+1; i++ )
        {
            firstPostPart = firstPostPart -> next;
        }
        
        currentReverseNode ->next = firstPostPart;      
        while(nextReverseNode!= firstPostPart)
        {
            preReverseNode = currentReverseNode;
            currentReverseNode = nextReverseNode;
            nextReverseNode = currentReverseNode->next;
            currentReverseNode->next = preReverseNode;
        }
        if(m!=1)
        {
            lastOfPrePart->next = currentReverseNode;
        }
        else
        {
            head = currentReverseNode;
        }
        return head;
    }
};