[数据结构与算法]数据结构与算法之二叉树遍历(JavaScript递归实现)

通过递归实现二叉树的遍历

二叉树的前序

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var preorderTraversal = function(root) {
    if (!root) return []
    const res = []
    order(root, res)
    return res;
};

var order = function(node,res){
    if(!node){
        return node;
    }
    res.push(node.val);
    order(node.left,res);
    order(node.right,res);
    return res;
}

中序

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var inorderTraversal = function(root) {
    if(!root){
        return [];
    }
    let res = [];
    order(root,res)
    return res;
};

var order = function(node,res){
    if(!node){
        return node;
    }

    order(node.left,res);
    res.push(node.val);
    order(node.right,res);
    return res;
}

后序遍历

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var postorderTraversal = function(root) {
    if(!root){
        return [];
    }
    let res = [];
    order(root,res);
    return res;
};

var order = function(node,res){
    if(!node){
        return node;
    }
    order(node.left,res);
    order(node.right,res);
    res.push(node.val);
    return res;
}

参考

1. leetcode postorder
2. leetcode preorder
3. leetcode inorder
4.代码随想录