236. Lowest Common Ancestor of a Binary Tree

Author: a-khakimov

leetcode-scala/src/main/scala/LeetCode75/BinaryTree_DFS/236. Lowest Common Ancestor of a Binary Tree.sc

@@ -0,0 +1,70 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(var _value: Int) {
+ *   var value: Int = _value
+ *   var left: TreeNode = null
+ *   var right: TreeNode = null
+ * }
+ */
+
+
+class TreeNode(_value: Int = 0, _left: TreeNode = null, _right: TreeNode = null) {
+  var value: Int = _value
+  var left: TreeNode = _left
+  var right: TreeNode = _right
+}
+
+object Solution {
+  // quick first solution - todo: make it better
+  def lowestCommonAncestor(root: TreeNode, p: TreeNode, q: TreeNode): TreeNode = {
+    var lca: TreeNode = null
+    def dfs(node: TreeNode): (Boolean, Boolean) = {
+      if (node != null) {
+        //println(s"[${node.value}]")
+        val foundP = node.value == p.value
+        val foundQ = node.value == q.value
+        val (frp, frq) = dfs(node.right)
+        val (flp, flq) = dfs(node.left)
+
+        // this is pzdc)
+        val found = {
+          if (frp && frq) { lca = node; true }
+          else if (flp && flq) { lca = node; true }
+          else if (frp && flq) { lca = node; true }
+          else if (flp && frq) { lca = node; true }
+          else if (frp && (node.value == q.value)) { lca = node; true }
+          else if (flp && (node.value == q.value)) { lca = node; true }
+          else if (frq && (node.value == p.value)) { lca = node; true }
+          else if (flq && (node.value == p.value)) { lca = node; true }
+          else false
+        }
+
+        if (found) (false, false) else (foundP || frp || flp, foundQ || frq || flq)
+      } else (false, false)
+    }
+    dfs(root)
+    lca
+  }
+}
+
+
+val tree1 = new TreeNode(3,
+  new TreeNode(5,
+    new TreeNode(6),
+    new TreeNode(7)
+  ),
+  new TreeNode(1,
+    new TreeNode(4),
+    new TreeNode(2,
+      new TreeNode(9),
+      new TreeNode(11,
+        new TreeNode(8),
+        new TreeNode(10)
+      )
+    )
+  )
+)
+
+Solution.lowestCommonAncestor(tree1, new TreeNode(11), new TreeNode(10)).value // 11
+Solution.lowestCommonAncestor(tree1, new TreeNode(8), new TreeNode(10)).value // 11
+Solution.lowestCommonAncestor(tree1, new TreeNode(7), new TreeNode(8)).value // 11