silvergoni.builder()

https://leetcode.com/problems/count-univalue-subtrees/ 1. 2022/05/12 시도 소요시간: 26분 class Solution { int counter = 0; public int countUnivalSubtrees(TreeNode root) { recursive(root); return counter; } private boolean recursive(TreeNode root) { if (root == null) { return true; } boolean l = recursive(root.left); boolean r = recursive(root.right); boolean c = false; if (root.left == null && root.rig..

https://leetcode.com/problems/symmetric-tree/ 3. 2022/05/11 시도 소요시간: 12분(iterative), 6분(recursive) // iterative class Solution { public boolean isSymmetric(TreeNode root) { if (root == null) { return true; } Queue queue = new LinkedList(); queue.offer(root); while(!queue.isEmpty()) { int size = queue.size(); Stack stack = new Stack(); for (int i=0; i= size - size/2) { TreeNode compare = stack.po..

https://leetcode.com/problems/maximum-depth-of-binary-tree/ 3. 2022/05/11 시도 소요시간: 1분(recursive, bottomup), 2분(recursive, topdown), 3분(iterative, dfs), 2분(iterative, bfs) // recursive - bottomup class Solution { public int maxDepth(TreeNode root) { return recursive(root); } private int recursive(TreeNode root) { if (root == null) { return 0; } int left = recursive(root.left); int right = recursi..

https://leetcode.com/problems/binary-tree-level-order-traversal/ 2. 2022/05/11 시도 소요시간: 4분(iterative), 5분(recursive) // iterative class Solution { public List levelOrder(TreeNode root) { List ret = new ArrayList(); if (root == null) { return ret; } Queue queue = new LinkedList(); queue.offer(root); while(!queue.isEmpty()) { int size = queue.size(); List inner = new ArrayList(); for (int i=0; i

https://leetcode.com/problems/binary-tree-postorder-traversal/ 1. 2022/05/11 시도 소요시간: 1분(recursive), 못품(iterative) // recursive class Solution { public List postorderTraversal(TreeNode root) { List ret = new ArrayList(); recursive(root, ret); return ret; } private void recursive(TreeNode root, List ret) { if (root == null) { return; } recursive(root.left, ret); recursive(root.right, ret); ret.ad..

https://leetcode.com/problems/binary-tree-inorder-traversal/ 3. 2022/05/10 시도 소요시간: 2분(recursive), 13분(iterative) // recursive class Solution { public List inorderTraversal(TreeNode root) { List ret = new ArrayList(); recursive(root, ret); return ret; } private void recursive(TreeNode root, List ret) { if (root == null) { return; } recursive(root.left, ret); ret.add(root.val); recursive(root.rig..

https://leetcode.com/problems/binary-tree-preorder-traversal/ 1. 2022/05/10 시도 소요시간: 7분(iterative), 3분(recursive) // iterative - preorder class Solution { public List preorderTraversal(TreeNode root) { List ret = new ArrayList(); if (root == null) { return ret; } LinkedList stack = new LinkedList(); stack.push(root); while(!stack.isEmpty()) { TreeNode node = stack.pop(); ret.add(node.val); if (n..

https://leetcode.com/problems/rotate-list/ 1. 2022/05/08 시도 소요시간: 12분 class Solution { public ListNode rotateRight(ListNode head, int k) { if (head == null) { return null; } int length = 0; ListNode current = head; while (current != null) { length++; current = current.next; } if (length == 1) { return head; } int remain = k%length; if (remain == 0) { return head; } ListNode prev = head; for (int..

https://leetcode.com/problems/copy-list-with-random-pointer/ 1. 2022/05/07 시도 소요시간: 21분( 공간복잡도 O(n)), 13분( 공간복잡도O(1)) // 공간복잡도 O(n) class Solution { public Node copyRandomList(Node head) { Map map = new HashMap(); Node dummyNode = new Node(0); Node dummyHead = dummyNode; Node current = head; while (current != null) { Node newNode = new Node(current.val); dummyNode.next = newNode; newNode.random ..

https://leetcode.com/problems/insert-into-a-sorted-circular-linked-list/ 1. 2022/05/07 시도 소요시간: 25분 class Solution { public Node insert(Node head, int insertVal) { if (head == null) { head = new Node(insertVal); head.next = head; return head; } Node prev = head; Node current = head; while (true) { current = current.next; if (current == head) { Node newNode = new Node(insertVal); prev.next = newN..