• https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
• 105. Construct Binary Tree from Preorder and Inorder Traversal

JavaScript 解答

var buildTree = function(preorder, inorder) {
    p = i = 0
    build = function(stop) {
        if (inorder[i] != stop) {
            var root = new TreeNode(preorder[p++])
            root.left = build(root.val)
            i++
            root.right = build(stop)
            return root
        }
        return null
    }
    return build()
};

Ruby 解答

def build_tree(preorder, inorder)
    if preorder.length==0
        return nil
    end
    root=TreeNode.new(preorder[0])
    mid=0
    while inorder[mid]!=preorder[0]
        mid+=1
    end
    root.left=build_tree(preorder[1...mid+1], inorder[0...mid])
    root.right=build_tree(preorder[mid+1...preorder.length], inorder[mid+1...inorder.length])
    return root
end