silvergoni.builder()

https://leetcode.com/problems/binary-search/ 1. 2022.01.17 시도 소요시간: 25분 class Solution { public int search(int[] nums, int target) { if (nums == null) { return -1; } return search(nums, target, 0, nums.length-1); } private int search(int[] nums, int target, int start, int end) { if (start > end ) { return -1; } int middle = (start + end)/2; if (target == nums[middle]) { return middle; } else if ..

https://leetcode.com/problems/path-sum/ 2. 2022/05/12 시도 소요시간: 8분(recursive-topdown), 8분(iterative-dfs) // recursive-topdown class Solution { boolean hasAnswer = false; int targetSum; public boolean hasPathSum(TreeNode root, int targetSum) { if (root == null) { return false; } this.targetSum = targetSum; recursive(root, 0); return hasAnswer; } private void recursive(TreeNode root, int sum) { if ..

https://leetcode.com/problems/reverse-integer/ 1. 2022.01.16 시도 소요시간: 10분 class Solution { public int reverse(int x) { if (-10 = 0) ? 1 : 1; int reversed = 0; while(x != 0) { int temp = (reversed * 10) + (x % 10); if (temp/10 != reversed) { //범위를 넘어버린 것 return 0; } reversed = temp; x = x/ 10; } return sign * reversed; } } 풀이 접근 과정 integer palindrome을 ..

https://leetcode.com/problems/palindrome-number/ 1. 2022.01.10 시도 소요시간: 5분(string) // string class Solution { public boolean isPalindrome(int x) { if (x < 0) { return false; } String str = x+""; int p = 0; int q = str.length() -1; while(p reversed) { reversed = reversed*10 + x%10; x = x/10; } return x == reversed || x == reversed/10; } } 알고리즘 정리노트: .leetcode(알고리즘 문제풀이 접근)

leetcode.com/problems/invert-binary-tree/ 2. 2022.01.09 시도 소요시간: 4분(recursive), 3분(iterative) // recursive class Solution { public TreeNode invertTree(TreeNode root) { recursive(root); return root; } public void recursive(TreeNode root) { if (root == null) { return; } recursive(root.left); recursive(root.right); TreeNode temp = root.left; root.left = root.right; root.right = temp; } } // iterati..

https://leetcode.com/problems/merge-two-binary-trees 2. 2021.01.09 시도 소요시간: 17분(recursive) // recursive class Solution { public TreeNode mergeTrees(TreeNode root1, TreeNode root2) { TreeNode ret = recursive(root1, root2); return ret; } private TreeNode recursive(TreeNode root1, TreeNode root2) { if (root1 == null) { return copyTreeNode(root2); } if (root2 == null) { return copyTreeNode(root1); }..

https://leetcode.com/problems/n-ary-tree-preorder-traversal/ 1. 2022.01.09 시도 소요시간: 5분(1분 구상, 4분 코딩,recursive), 9분(iterative) // recursive class Solution { public List preorder(Node root) { List output = new ArrayList(); recursive(root, output); return output; } private void recursive(Node root, List output) { if (root == null) { return; } output.add(root.val); for (Node child: root.children) { ..

https://leetcode.com/problems/n-ary-tree-postorder-traversal/ 1. 2022.01.05 시도 소요시간: 9분(3분 구상, 6분 코딩, recursive), 17분(iterative) // recursive class Solution { public List postorder(Node root) { List ret = new ArrayList(); if (root == null) { return ret; } recursive(root, ret); ret.add(root.val); return ret; } private void recursive(Node root, List ret) { if (root == null) { return; } for(Node ch..

https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/ 1. 2022.01.05 시도 소요시간: 9분(map), 9분(array) # map class Solution { public int[] twoSum(int[] numbers, int target) { Map temp = new HashMap(); for(int x=0; x

https://leetcode.com/problems/two-sum/ 2. 2022.01.03 시도 소요시간: 34분(27분 실패, 7분 구상 및 코딩, n^2복잡도), 5분(map이용) // n^2 class Solution { public int[] twoSum(int[] nums, int target) { for (int x=0; x