BinaryTreeInorderTraversal
BinaryTreeInorderTraversal.java 源码
package datastructure.tree.leetcode;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
/**
* @author roseduan
* @time 2020/9/14 10:03 下午
* @description 二叉树的中序遍历
*/
public class BinaryTreeInorderTraversal {
private final List<Integer> res = new ArrayList<>();
/**
* 递归的方式
* 运行结果：通过，速度击败 100%
*/
public List<Integer> inorderTraversal(TreeNode root) {
if (root == null) {
return res;
}
inorderTraversal(root.left);
res.add(root.val);
inorderTraversal(root.right);
return res;
}
/**
* 迭代的方式，使用一个栈，手动实现递归的效果
*/
public List<Integer> inorderTraversal2(TreeNode root) {
List<Integer> res = new ArrayList<>();
Stack<TreeNode> stack = new Stack<>();
TreeNode cur = root;
while (cur != null || !stack.empty()) {
while (cur != null) {
stack.push(cur);
cur = cur.left;
}
cur = stack.pop();
res.add(cur.val);
cur = cur.right;
}
return res;
}
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int val) { this.val = val; }
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
}
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