LeetCode OJ - Reverse Linked List II

Reverse a linked list from position m to n. Do it in-place and in one-pass.

For example:

Given 

1->2->3->4->5->NULL

, m = 2 and n =
4,

return 

1->4->3->2->5->NULL

.

Note:

Given m, n satisfy the following condition:

1 ≤ m ≤ n ≤ length of list.

/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *reverseBetween(ListNode *head, int m, int n) {
if(!head) return NULL;
ListNode *cur = head;
ListNode *front, *tail;
stack<int> st;

int start = 1;
while(cur) {
if(start == m) {
front = cur;
}
if(start >= m && start <= n) {
st.push(cur->val);
}
if(start == n) {
break;
}
start++;
cur = cur->next;
}

while(!st.empty()) {
front->val = st.top();
st.pop();
front = front->next;
}
return head;
}
};