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Author: jimit105

1387-find-elements-in-a-contaminated-binary-tree/README.md

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+<p>Given a binary tree with the following rules:</p>
+
+<ol>
+	<li><code>root.val == 0</code></li>
+	<li>For any <code>treeNode</code>:
+	<ol type="a">
+		<li>If <code>treeNode.val</code> has a value <code>x</code> and <code>treeNode.left != null</code>, then <code>treeNode.left.val == 2 * x + 1</code></li>
+		<li>If <code>treeNode.val</code> has a value <code>x</code> and <code>treeNode.right != null</code>, then <code>treeNode.right.val == 2 * x + 2</code></li>
+	</ol>
+	</li>
+</ol>
+
+<p>Now the binary tree is contaminated, which means all <code>treeNode.val</code> have been changed to <code>-1</code>.</p>
+
+<p>Implement the <code>FindElements</code> class:</p>
+
+<ul>
+	<li><code>FindElements(TreeNode* root)</code> Initializes the object with a contaminated binary tree and recovers it.</li>
+	<li><code>bool find(int target)</code> Returns <code>true</code> if the <code>target</code> value exists in the recovered binary tree.</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2019/11/06/untitled-diagram-4-1.jpg" style="width: 320px; height: 119px;" />
+<pre>
+<strong>Input</strong>
+[&quot;FindElements&quot;,&quot;find&quot;,&quot;find&quot;]
+[[[-1,null,-1]],[1],[2]]
+<strong>Output</strong>
+[null,false,true]
+<strong>Explanation</strong>
+FindElements findElements = new FindElements([-1,null,-1]); 
+findElements.find(1); // return False 
+findElements.find(2); // return True </pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2019/11/06/untitled-diagram-4.jpg" style="width: 400px; height: 198px;" />
+<pre>
+<strong>Input</strong>
+[&quot;FindElements&quot;,&quot;find&quot;,&quot;find&quot;,&quot;find&quot;]
+[[[-1,-1,-1,-1,-1]],[1],[3],[5]]
+<strong>Output</strong>
+[null,true,true,false]
+<strong>Explanation</strong>
+FindElements findElements = new FindElements([-1,-1,-1,-1,-1]);
+findElements.find(1); // return True
+findElements.find(3); // return True
+findElements.find(5); // return False</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2019/11/07/untitled-diagram-4-1-1.jpg" style="width: 306px; height: 274px;" />
+<pre>
+<strong>Input</strong>
+[&quot;FindElements&quot;,&quot;find&quot;,&quot;find&quot;,&quot;find&quot;,&quot;find&quot;]
+[[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]]
+<strong>Output</strong>
+[null,true,false,false,true]
+<strong>Explanation</strong>
+FindElements findElements = new FindElements([-1,null,-1,-1,null,-1]);
+findElements.find(2); // return True
+findElements.find(3); // return False
+findElements.find(4); // return False
+findElements.find(5); // return True
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>TreeNode.val == -1</code></li>
+	<li>The height of the binary tree is less than or equal to <code>20</code></li>
+	<li>The total number of nodes is between <code>[1, 10<sup>4</sup>]</code></li>
+	<li>Total calls of <code>find()</code> is between <code>[1, 10<sup>4</sup>]</code></li>
+	<li><code>0 &lt;= target &lt;= 10<sup>6</sup></code></li>
+</ul>

1387-find-elements-in-a-contaminated-binary-tree/solution.py

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+# Approach 1: DFS
+
+# Time: 
+# constructor: O(n)
+# find(): O(1)
+
+# Space: O(n)
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+class FindElements:
+
+    def __init__(self, root: Optional[TreeNode]):
+        self.seen = set()
+        self.dfs(root, 0)
+
+    def find(self, target: int) -> bool:
+        return target in self.seen
+
+    def dfs(self, current_node, current_value):
+        if current_node is None:
+            return
+        
+        self.seen.add(current_value)
+        self.dfs(current_node.left, current_value * 2 + 1)
+        self.dfs(current_node.right, current_value * 2 + 2)
+        
+
+
+# Your FindElements object will be instantiated and called as such:
+# obj = FindElements(root)
+# param_1 = obj.find(target)