Halo World

https://leetcode.com/problems/merge-two-binary-trees/ class Solution { public TreeNode mergeTrees(TreeNode root1, TreeNode root2) { TreeNode head = root1; if(root1==null && root2==null) return null; if(root1==null && root2!=null) return root2; if(root1!=null && root2==null) return root1; root1.val+=root2.val; root1.left = mergeTrees(root1.left, root2.left); root1.right = mergeTrees(root1.right, ..

https://leetcode.com/problems/count-binary-substrings/ //풀이 봄 class Solution { /*public int countBinarySubstrings(String s) { int[] groups = new int[s.length()]; int idx = 0; groups[0]=1; for(int i=1;i

https://leetcode.com/problems/symmetric-tree/ class Solution { public boolean isSymmetric(TreeNode root) { return isMirror(root.right, root.left); } private boolean isMirror(TreeNode n1, TreeNode n2){ if(n1==null || n2==null) return n1==n2; return (n1.val == n2.val && isMirror(n1.left, n2.right) && isMirror(n1.right, n2.left)); } }

https://leetcode.com/problems/invert-binary-tree/ class Solution { public TreeNode invertTree(TreeNode root) { TreeNode head= root; if(root!=null) invert(root); return head; } private void invert(TreeNode n1) { if(n1==null) return; invert(n1.right); invert(n1.left); TreeNode tmp = n1.right; n1.right = n1.left; n1.left = tmp; } }

https://leetcode.com/problems/diameter-of-binary-tree/ class Solution { int max=0; public int diameterOfBinaryTree(TreeNode root) { int left = findDepth(root.left); int right = findDepth(root.right); return Math.max(left + right, max); } int findDepth(TreeNode node) { if(node==null) return 0; int left = findDepth(node.left); int right = findDepth(node.right); max = Math.max(left + right, max); r..