p226

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LeetCode P226 Invert Binary Tree 题解

1.题目：

Invert a binary tree.

题意：

将一个二叉树反转

2.解题思路:

跟前面一题差不多啦~遍历的时候交换左右节点就好

3.代码

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package leetcode;

package leetcode;

import tool.TreeNode;

/**
 * 
 * @author ZhangMengRou
 *
 */
public class p226 {

	public static void main(String[] args) {
		// Scanner in = new Scanner(System.in);
		// String a = in.nextLine();
		
		//测试数据
		TreeNode froot = null;
		froot = new TreeNode(4);
		TreeNode n2 = new TreeNode(2);
		TreeNode n3 = new TreeNode(3);
		TreeNode n9 = new TreeNode(9);
		TreeNode n1 = new TreeNode(1);
		TreeNode n6 = new TreeNode(6);
		TreeNode n7 = new TreeNode(7);
		froot.left = n2;
		froot.right = n7;
		n2.left = n1;
		n2.right = n3;
		n7.left = n6;
		n7.right = n9;
		TreeNode ans = invertTree(froot);
		Check(ans);
		// System.out.print(ans);
	}

	public static TreeNode invertTree(TreeNode root) {

		TreeNode ans = root;
		DFS(ans);

		return ans;
	}

	public static void DFS(TreeNode t) {
		// System.out.print("mmmm "+t.val+"  "+count+"\n");
		if (t == null || (t.left == null && t.right == null)) {
			return;
		}
		TreeNode c = t.left;
		t.left = t.right;
		t.right = c;
		if (!(t.left == null)) {

			DFS(t.left);
		}

		if (!(t.right == null)) {

			DFS(t.right);
		}

		return;
	}

	public static void Check(TreeNode t) {
		System.out.print("mmmm " + t.val + "  " + "\n");
		if (t == null || (t.left == null && t.right == null)) {
			return;
		}
		if (!(t.left == null)) {
			System.out.print("L " + t.left.val + "  " + "\n");

			Check(t.left);
		}

		if (!(t.right == null)) {

			System.out.print("R " + t.right.val + "  " + "\n");
			Check(t.right);
		}

		return;
	}

}



//
//public class TreeNode {
//
//		public int val;
//	    public TreeNode left;
//	    public TreeNode right;
//	    public TreeNode(int x) { val = x; }
//	
//}


4.一些总结：

我会反转二叉树~听起来萌萌哒