hello-algo/codes/ruby/chapter_backtracking/preorder_traversal_i_compact.rb

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=begin
File: preorder_traversal_i_compact.rb
Created Time: 2024-05-22
Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
=end
require_relative '../utils/tree_node'
require_relative '../utils/print_util'
### 前序遍历:例题一 ###
def pre_order(root)
return unless root
# 记录解
$res << root if root.val == 7
pre_order(root.left)
pre_order(root.right)
end
### Driver Code ###
if __FILE__ == $0
root = arr_to_tree([1, 7, 3, 4, 5, 6, 7])
puts "\n初始化二叉树"
print_tree(root)
# 前序遍历
$res = []
pre_order(root)
puts "\n输出所有值为 7 的节点"
p $res.map { |node| node.val }
end