silvergoni.builder()

https://leetcode.com/problems/check-completeness-of-a-binary-tree/ 1. 2022.02.21 시도 소요시간: 79분(완전 이진트리 이해 시간 + 코딩) class Solution { public boolean isCompleteTree(TreeNode root) { if (root == null) { return true; } LinkedList queue = new LinkedList(); queue.offer(root); int depth = 0; while(!queue.isEmpty()) { int limit = queue.size(); for (int i=0; i

https://leetcode.com/problems/distribute-coins-in-binary-tree/ 1. 2022.02.20 시도 소요시간: 76분(36분 구상, 40분 풀이) class Solution { public int distributeCoins(TreeNode root) { return traverse(root); } private int traverse(TreeNode root) { int left = 0; int leftv = 0; if (root.left != null) { left = traverse(root.left); leftv = root.left.val; } int right = 0; int rightv = 0; if (root.right != null) { righ..

https://leetcode.com/problems/univalued-binary-tree/ 1. 2022.02.20 시도 소요시간: 4분 class Solution { public boolean isUnivalTree(TreeNode root) { return traverse(root, root.val); } private boolean traverse(TreeNode root, int value) { boolean ret = root.val == value; if (root.left != null) { ret = ret && traverse(root.left, value); } if (root.right != null) { ret = ret && traverse(root.right, value); ..

https://leetcode.com/problems/range-sum-of-bst/ 1. 2022.02.19 시도 소요시간: 12분(3분 문제이해 및 구상, 9분 코딩, recursive), 2분(iterative) class Solution { public int rangeSumBST(TreeNode root, int low, int high) { if (root == null) { return 0; } int sum = 0; sum += rangeSumBST(root.left, low, high); sum += rangeSumBST(root.right, low, high); if (low

https://leetcode.com/problems/partition-list/ 1. 2022.02.06 시도 소요시간: 22분 class Solution { public ListNode partition(ListNode head, int x) { if (head == null) { return null; } ListNode start = new ListNode(200); start.next = head; ListNode prev = start; ListNode ret = start; ListNode current = head; while(current != null) { if (current.val < x && start.next == current) { start = current; prev = c..

https://leetcode.com/problems/find-bottom-left-tree-value/ 1. 2022.02.06 시도 소요시간: 18분(전역변수), 10분(bfs) // 전역변수 class Solution { private int maxDepth = -1; private int max = Integer.MIN_VALUE; public int findBottomLeftValue(TreeNode root) { dfs(root, 0); return max; } private void dfs(TreeNode root, int depth) { if (root == null) { return; } dfs(root.left, depth+1); dfs(root.right, depth+1); if (r..

https://leetcode.com/problems/swap-nodes-in-pairs/ 1. 2022.02.05 시도 소요시간: 10분 class Solution { public ListNode swapPairs(ListNode head) { if (head == null || head.next == null) { return head; } ListNode prev = new ListNode(); ListNode ret = prev; prev.next = head; while (prev.next != null && prev.next.next != null) { ListNode temp = head.next; head.next = temp.next; temp.next = head; prev.next =..

https://leetcode.com/problems/hand-of-straights/ 1. 2022.02.05 시도 소요시간: 35분(11분 구상, 24분 코딩) class Solution { public boolean isNStraightHand(int[] hand, int groupSize) { if ((hand.length % groupSize) != 0) { return false; } // sort Arrays.sort(hand); List nums = new ArrayList(); List counts = new ArrayList(); int prev = -1; for (int i=0; i< hand.length; i++) { if (prev == hand[i]) { counts.set(co..

https://leetcode.com/problems/binary-tree-pruning/ 1. 2022.02.05 시도 소요시간: 5분 // dfs class Solution { public TreeNode pruneTree(TreeNode root) { root = dfs(root); return root; } public TreeNode dfs(TreeNode root) { if (root == null) { return null; } TreeNode left = dfs(root.left); if (left == null) { root.left = null; } TreeNode right = dfs(root.right); if (right == null) { root.right = null; } i..

https://leetcode.com/problems/find-largest-value-in-each-tree-row/ 1. 2022.01.30 시도 소요시간: 30분 이상(다른 일때문에 측정x) class Solution { public List largestValues(TreeNode root) { LinkedList output = new LinkedList(); if (root == null) { return output; } LinkedList queue = new LinkedList(); LinkedList depthQueue = new LinkedList(); queue.offer(root); depthQueue.offer(0); while(!queue.isEmpty()) { TreeNode..