//反轉一個單鏈表。 -----迭代
//
// 示例: 
//
// 輸入: 1->2->3->4->5->NULL
//輸出: 5->4->3->2->1->NULL 
//
// 進階: 
//你可以迭代或遞迴地反轉連結串列。你能否用兩種方法解決這道題？ 
// Related Topics 連結串列

package leetcode.editor.cn;

import com.example.demo.ArrayConvertLinkedList;
import com.example.demo.ListNode;

import java.util.Stack;

//Java：反轉連結串列
public class P206ReverseLinkedList {
    public static void main(String[] args) {
        Solution solution = new P206ReverseLinkedList().new Solution();
        // TO TEST
        int[] array = {1, 2, 3, 4, 5};
        ListNode head = ArrayConvertLinkedList.arrayToNode(array);
        head = solution.reverseList(head);
        ArrayConvertLinkedList.printNode(head);

    }
    //leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     * int val;
     * ListNode next;
     * ListNode(int x) { val = x; }
     * }
     */
    class Solution {
        public ListNode reverseList(ListNode head) {
            ListNode prev = null;
            ListNode curr = head;
            while (curr != null) {
                ListNode nextTemp = curr.next;
                curr.next = prev;
                prev = curr;
                curr = nextTemp;
            }
            return prev;
        }
    }
//leetcode submit region end(Prohibit modification and deletion)

}