链表反转简单算法

版权声明：本文为博主原创文章，转载希望能注明出处，感谢。 https://blog.csdn.net/u010126792/article/details/82427092

链表反转java：

public class Demo12 {

	public static void main(String[] args) {
		Node node1 = new Node(1, null);
		Node node2 = new Node(2, null);
		Node node3 = new Node(3, null);
		Node node4 = new Node(4, null);
		Node node5 = new Node(5, null);
		Node node6 = new Node(6, null);
		Node node7 = new Node(7, null);
		node1.next= node2;
		node2.next = node3;
		node3.next = node4;
		node4.next = node5;
		node5.next = node6;
		node6.next = node7;
		node7.next = null;
		Node newnode = reverse1(node1);
		System.out.println(newnode.index);

	}
	
	public static Node reverse1(Node node) {
		if (node == null || node.next == null) {
			return node;
		}
		
		Node nodecurr = node;
		Node nodepre = null;
		while (nodecurr != null) {
			Node next = nodecurr.next;
			nodecurr.next = nodepre;
			nodepre = nodecurr;
			nodecurr = next;
		}
		
		return nodepre;
	}
	

	public Node reverse2(Node node, Node prev) {
	    if (node.next == null) {
	      node.next = prev;
	      return node;
	    } else {
	      Node re = reverse2(node.next, node);
	      node.next = prev;
	      return re;
	    }
	}

}

class Node {
    int index;
    Node next;

    public Node(int index, Node next) {
      this.index = index;
      this.next = next;
    }
  }

原理解释看图:

上图是非递归算法的思路，把前一个节点指向当前节点的下一个节点。

递归算法的思路类似，找到最后一个节点，它的next等于null，则把前一个节点作为它的next节点。