I’m trying to reverse a segment of a singly linked list in C++ using the following function. However, I’m seeing unexpected behavior when the value of left is 2. Specifically, the first while loop executes even though the condition should evaluate to false.

Here is my code:

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseBetween(ListNode* head, int left, int right) {
        ListNode* l = head, *r = head;
        while (left - 2 != 0) {
            cout << left << endl;
            l = l->next;
            left--;
        }
        while (right) {
            r = r->next;
            right--;
        }

        ListNode* p = nullptr, *q = l->next;
        while (q != r) {
            ListNode* tmp = q->next;
            q->next = p;
            p = q;
            q = tmp;
        }
        l->next->next = q;
        l->next = p;
        return head;
    }
};


Input: 
head = [1,2,3,5,5]
left = 2
right = 4

Stdout:
1
0

There's only one cout statement i.e in the first while loop but for this input it should never go inside. I can try other ways and I know other solutions to this problem I only want to know why is it showing this abnormal behaviour.