LeetCode-in-Java

1261. Find Elements in a Contaminated Binary Tree

Medium

Given a binary tree with the following rules:

1. root.val == 0
2. If treeNode.val == x and treeNode.left != null, then treeNode.left.val == 2 * x + 1
3. If treeNode.val == x and treeNode.right != null, then treeNode.right.val == 2 * x + 2

Now the binary tree is contaminated, which means all treeNode.val have been changed to -1.

Implement the FindElements class:

• FindElements(TreeNode* root) Initializes the object with a contaminated binary tree and recovers it.
• bool find(int target) Returns true if the target value exists in the recovered binary tree.

Example 1:

Input [“FindElements”,”find”,”find”] [[[-1,null,-1]],[1],[2]]

Output: [null,false,true]

Explanation:

FindElements findElements = new FindElements([-1,null,-1]); 
findElements.find(1); // return False 
findElements.find(2); // return True

Example 2:

Input [“FindElements”,”find”,”find”,”find”] [[[-1,-1,-1,-1,-1]],[1],[3],[5]]

Output: [null,true,true,false]

Explanation:

FindElements findElements = new FindElements([-1,-1,-1,-1,-1]); 
findElements.find(1); // return True 
findElements.find(3); // return True 
findElements.find(5); // return False

Example 3:

Input [“FindElements”,”find”,”find”,”find”,”find”] [[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]]

Output: [null,true,false,false,true]

Explanation:

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

Constraints:

• TreeNode.val == -1
• The height of the binary tree is less than or equal to 20
• The total number of nodes is between [1, 104]
• Total calls of find() is between [1, 104]
• 0 <= target <= 106

Solution

import com_github_leetcode.TreeNode;
import java.util.HashMap;

/*
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class FindElements {
    private final HashMap<Integer, Integer> map = new HashMap<>();

    public FindElements(TreeNode root) {
        helper(root, 0);
    }

    private void helper(TreeNode root, int x) {
        if (root == null) {
            return;
        }
        root.val = x;
        map.put(x, 0);
        helper(root.left, 2 * x + 1);
        helper(root.right, 2 * x + 2);
    }

    public boolean find(int target) {
        return map.containsKey(target);
    }
}

/*
 * Your FindElements object will be instantiated and called as such:
 * FindElements obj = new FindElements(root);
 * boolean param_1 = obj.find(target);
 */

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