refactor 1644

fishercoder1534 · fishercoder1534 · commit dba2ab08896e · 2021-10-30T15:34:25.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_1644.java b/src/main/java/com/fishercoder/solutions/_1644.java
@@ -48,6 +48,9 @@ private TreeNode dfs(TreeNode root, TreeNode p, TreeNode q) {
     }
 
     public static class Solution2 {
+        /**
+         * This satisfies the follow-up question: Can you find the LCA traversing the tree, without checking nodes existence?
+         */
         int found = 0;
 
         public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
@@ -57,15 +60,15 @@ public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
 
         private TreeNode lca(TreeNode root, TreeNode p, TreeNode q) {
             if (root == null) {
-                return root;
+                return null;
             }
             TreeNode left = lca(root.left, p, q);
             TreeNode right = lca(root.right, p, q);
             if (root == p || root == q) {
                 found++;
                 return root;
             }
-            return left == null ? right : right == null ? left : root;
+            return (left != null && right != null) ? root : left != null ? left : right;
         }
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -48,6 +48,9 @@ private TreeNode dfs(TreeNode root, TreeNode p, TreeNode q) {`
`48`	`48`	`}`
`49`	`49`
`50`	`50`	`public static class Solution2 {`
	`51`	`+ /**`
	`52`	`+ * This satisfies the follow-up question: Can you find the LCA traversing the tree, without checking nodes existence?`
	`53`	`+ */`
`51`	`54`	`int found = 0;`
`52`	`55`
`53`	`56`	`public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {`
`@@ -57,15 +60,15 @@ public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {`
`57`	`60`
`58`	`61`	`private TreeNode lca(TreeNode root, TreeNode p, TreeNode q) {`
`59`	`62`	`if (root == null) {`
`60`		`- return root;`
	`63`	`+ return null;`
`61`	`64`	`}`
`62`	`65`	`TreeNode left = lca(root.left, p, q);`
`63`	`66`	`TreeNode right = lca(root.right, p, q);`
`64`	`67`	`if (root == p \|\| root == q) {`
`65`	`68`	`found++;`
`66`	`69`	`return root;`
`67`	`70`	`}`
`68`		`- return left == null ? right : right == null ? left : root;`
	`71`	`+ return (left != null && right != null) ? root : left != null ? left : right;`
`69`	`72`	`}`
`70`	`73`	`}`
`71`	`74`	`}`