找二叉树中任意两个节点的最近的公共父节点

大概分为两种情况，一种是pq两个节点在树或者子树的同一边

package test;

public class SmallCommonParent {

	public static void main(String[] args) {
		/*
		 * 第一种情况，p和q在root的两边
		 *  		root
		 *  		/	\
		 *  		p	a
		 *  			 \
		 *  			 q
		 * */ 
//		TreeNode p = new TreeNode("p");
//		TreeNode q = new TreeNode("q");
//		TreeNode a = new TreeNode("a",null,q);
//		TreeNode rootNode = new TreeNode("root", p, a);
		
		/*
		 * 第二种情况，p和q在root的同一边
		 *  		root
		 *  		/	\
		 *  		a	p
		 *  	   /	 \
		 *  	  b		 q
		 * */ 
		TreeNode q = new TreeNode("q");
		TreeNode p = new TreeNode("p",null,q);
		TreeNode b = new TreeNode("b");
		TreeNode a = new TreeNode("a",b,null);
		TreeNode rootNode = new TreeNode("root", a, p);
		
		TreeNode loNode = lowestCommonAncestor(rootNode, p, q);
		System.out.println("获取到的最近的父节点：" + loNode.getNodeName());
	}

	public static TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
		if (root == null || root == p || root == q)
			return root;
		TreeNode left = lowestCommonAncestor(root.left, p, q);
		TreeNode right = lowestCommonAncestor(root.right, p, q);
		if (left != null && right != null) {
			return root;
		}
		if (left != null) {
			return left;
		} else {
			return right;
		}

	}

	static class TreeNode {
		private String nodeName;
		private TreeNode left;
		private TreeNode right;

		public TreeNode(String nodeName, TreeNode left, TreeNode right) {
			super();
			this.nodeName = nodeName;
			this.left = left;
			this.right = right;
		}

		public TreeNode(String nodeName) {
			this.nodeName = nodeName;
		}

		public String getNodeName() {
			return nodeName;
		}

		public void setNodeName(String nodeName) {
			this.nodeName = nodeName;
		}

		public TreeNode getLeft() {
			return left;
		}

		public void setLeft(TreeNode left) {
			this.left = left;
		}

		public TreeNode getRight() {
			return right;
		}

		public void setRight(TreeNode right) {
			this.right = right;
		}

	}

}