919. Complete Binary Tree Inserter - Medium
A?complete?binary tree is a binary tree in which every level,except possibly the last,is completely filled,and all nodes are as far left as possible. Write a data structure?
? Example 1: Input: inputs = ["CBTInserter","insert","get_root"],inputs = [[[1]],[2],[]] Output: [null,1,[1,2]]
Example 2: Input: inputs = ["CBTInserter",inputs = [[[1,2,3,4,5,6]],[7],[8],[]] Output: [null,6,7,8]]
? Note:
? M1:? ref:?https://leetcode.com/problems/complete-binary-tree-inserter/discuss/178424/C%2B%2BJavaPython-O(1)-Insert 以bfs的顺序,用List存tree nodes:tree[i]的左孩子tree[2i+1]、右孩子tree[2i+2] 当insert第n个node时,可以通过index找到它的parent: tree[(n-1)/2] initialization: time = O(n),space = O(n) insert: time = O(1),space = O(1) get_root: time = O(1),space = O(1) /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class CBTInserter { List<TreeNode> tree; TreeNode root; public CBTInserter(TreeNode root) { tree = new ArrayList<>(); this.root = root; tree.add(root); for(int i = 0; i < tree.size(); i++) { if(tree.get(i).left != null) { tree.add(tree.get(i).left); } if(tree.get(i).right != null) { tree.add(tree.get(i).right); } } } public int insert(int v) { int size = tree.size(); TreeNode node = new TreeNode(v); tree.add(node); if(size % 2 == 0) { tree.get((size - 1) / 2).right = node; } else { tree.get((size - 1) / 2).left = node; } return tree.get((size - 1) / 2).val; } public TreeNode get_root() { return tree.get(0); } } /** * Your CBTInserter object will be instantiated and called as such: * CBTInserter obj = new CBTInserter(root); * int param_1 = obj.insert(v); * TreeNode param_2 = obj.get_root(); */ ? M2: 用queue存 ref:?https://leetcode.com/problems/complete-binary-tree-inserter/discuss/178427/Java-BFS-straightforward-code-two-methods-Initialization-and-insert-time-O(1)-respectively.
initialization: time = O(n),space = O(1) /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class CBTInserter { Queue<TreeNode> q; TreeNode root; public CBTInserter(TreeNode root) { this.root = root; q = new LinkedList<>(); q.offer(root); while(q.peek().left != null && q.peek().right != null) { q.offer(q.peek().left); q.offer(q.peek().right); q.poll(); } } public int insert(int v) { TreeNode node = q.peek(); if(node.left == null) { node.left = new TreeNode(v); } else { node.right = new TreeNode(v); q.offer(node.left); q.offer(node.right); q.poll(); } return node.val; } public TreeNode get_root() { return root; } } /** * Your CBTInserter object will be instantiated and called as such: * CBTInserter obj = new CBTInserter(root); * int param_1 = obj.insert(v); * TreeNode param_2 = obj.get_root(); */ (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |