04月
01

二叉树中序遍历

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二叉树中序遍历

二叉树中序遍历：先遍历左子树，然后访问根节点，最后遍历右子树
二叉树中序遍历

递归实现中序遍历(Java）

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> result = new ArrayList<Integer>();
        pre(root,result);
        return result;
    }
    
    public void pre(TreeNode root, List<Integer> result){
        if(root == null){
            return;
        }
        pre(root.left,result);
        result.add(root.val);
        pre(root.right,result);
    }
}

堆栈迭代实现中序遍历(Java)

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> result = new ArrayList<Integer>();
        Stack<TreeNode> stack = new Stack<TreeNode>();
        TreeNode curr = root;
        while(curr != null || !stack.isEmpty()){
            while(curr != null){
                stack.push(curr);
                curr = curr.left;
            }
            curr = stack.pop();
            result.add(curr.val);
            curr = curr.right;
        }
        return result;
    }
}
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