{"id":22513986,"url":"https://github.com/emahtab/binary-tree-level-order-traversal-ii","last_synced_at":"2026-01-08T03:05:45.370Z","repository":{"id":79525313,"uuid":"263300263","full_name":"eMahtab/binary-tree-level-order-traversal-ii","owner":"eMahtab","description":"Binary Tree Level Order Traversal","archived":false,"fork":false,"pushed_at":"2020-05-12T10:11:14.000Z","size":4,"stargazers_count":1,"open_issues_count":0,"forks_count":0,"subscribers_count":1,"default_branch":"master","last_synced_at":"2025-02-02T03:26:16.862Z","etag":null,"topics":["bfs","binary-tree","binary-tree-traversal","leetcode","problem-solving"],"latest_commit_sha":null,"homepage":"","language":null,"has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":null,"status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/eMahtab.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":null,"code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2020-05-12T10:05:25.000Z","updated_at":"2020-05-12T10:12:26.000Z","dependencies_parsed_at":"2023-05-10T17:00:54.047Z","dependency_job_id":null,"html_url":"https://github.com/eMahtab/binary-tree-level-order-traversal-ii","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/eMahtab%2Fbinary-tree-level-order-traversal-ii","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/eMahtab%2Fbinary-tree-level-order-traversal-ii/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/eMahtab%2Fbinary-tree-level-order-traversal-ii/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/eMahtab%2Fbinary-tree-level-order-traversal-ii/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/eMahtab","download_url":"https://codeload.github.com/eMahtab/binary-tree-level-order-traversal-ii/tar.gz/refs/heads/master","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":245952375,"owners_count":20699476,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["bfs","binary-tree","binary-tree-traversal","leetcode","problem-solving"],"created_at":"2024-12-07T03:15:29.265Z","updated_at":"2026-01-08T03:05:45.360Z","avatar_url":"https://github.com/eMahtab.png","language":null,"funding_links":[],"categories":[],"sub_categories":[],"readme":"# Binary Tree Level Order Traversal II\n## https://leetcode.com/problems/binary-tree-level-order-traversal-ii\n\nGiven a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).\n```\nFor example:\nGiven binary tree [3,9,20,null,null,15,7],\n    3\n   / \\\n  9  20\n    /  \\\n   15   7\nreturn its bottom-up level order traversal as:\n[\n  [15,7],\n  [9,20],\n  [3]\n]\n```\n# Implementation 1 : \n```java\n/**\n * Definition for a binary tree node.\n * public class TreeNode {\n *     int val;\n *     TreeNode left;\n *     TreeNode right;\n *     TreeNode() {}\n *     TreeNode(int val) { this.val = val; }\n *     TreeNode(int val, TreeNode left, TreeNode right) {\n *         this.val = val;\n *         this.left = left;\n *         this.right = right;\n *     }\n * }\n */\nclass Solution {\n    public List\u003cList\u003cInteger\u003e\u003e levelOrderBottom(TreeNode root) {\n        List\u003cList\u003cInteger\u003e\u003e res = new ArrayList\u003c\u003e();\n        if(root == null)\n           return res;\n        Queue\u003cTreeNode\u003e q = new LinkedList\u003c\u003e();\n        q.offer(root);\n        while(!q.isEmpty()) {\n            int size = q.size();\n            List\u003cInteger\u003e level = new ArrayList\u003c\u003e();\n            for(int i = 1; i \u003c= size; i++) {\n                TreeNode current = q.poll();\n                level.add(current.val);\n                if(current.left != null)\n                    q.offer(current.left);\n                if(current.right != null)\n                    q.offer(current.right);\n            }\n            res.add(level);\n        }\n        Collections.reverse(res);\n        return res;\n    }\n}\n```\n\n# Implementation 2 :\n```java\n/**\n * Definition for a binary tree node.\n * public class TreeNode {\n *     int val;\n *     TreeNode left;\n *     TreeNode right;\n *     TreeNode(int x) { val = x; }\n * }\n */\nclass Solution {\n    public List\u003cList\u003cInteger\u003e\u003e levelOrderBottom(TreeNode root) {\n        List\u003cList\u003cInteger\u003e\u003e result = new ArrayList\u003cList\u003cInteger\u003e\u003e();\n        if(root == null){\n            return result;\n        }\n        Queue\u003cTreeNode\u003e queue = new ArrayDeque\u003cTreeNode\u003e();\n        queue.offer(root);\n        while(!queue.isEmpty()){\n            int size = queue.size();\n            List\u003cInteger\u003e level = new ArrayList\u003cInteger\u003e();\n            for(int i = 0; i \u003c size; i++){\n                TreeNode node = queue.poll();\n                level.add(node.val);\n                if(node.left != null)\n                    queue.offer(node.left);\n                if(node.right != null)\n                    queue.offer(node.right);\n            }\n          result.add(0,level);\n        }\n        return result;\n    }\n}\n```\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Femahtab%2Fbinary-tree-level-order-traversal-ii","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Femahtab%2Fbinary-tree-level-order-traversal-ii","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Femahtab%2Fbinary-tree-level-order-traversal-ii/lists"}