题解 | #二叉树的中序遍历#

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型一维数组
     */
    public int[] inorderTraversal (TreeNode root) {
        // write code here
        //左中 右
        ArrayList<Integer> temp = new ArrayList<Integer>();
        inOrder(root,temp);
        int[] result = new int[temp.size()];
        for(int i = 0;i<result.length;i++){
            result[i] = temp.get(i);
        }
        return result;
    }
    private void inOrder(TreeNode node, ArrayList<Integer> result){
        if(node == null){
            return;
        }
        inOrder(node.left, result);
        result.add(node.val);
        inOrder(node.right, result);
    }
}