Validate Binary Tree Nodes
You have n
binary tree nodes numbered from 0
to n - 1
where node i
has two children leftChild[i]
and rightChild[i]
, return true
if and only if all the given nodes form exactly one valid binary tree.
If node i
has no left child then leftChild[i]
will equal -1
, similarly for the right child.
Note that the nodes have no values and that we only use the node numbers in this problem.
Example 1:

Input: n = 4, leftChild = [1,-1,3,-1], rightChild = [2,-1,-1,-1]
Output: true
Example 2:

Input: n = 4, leftChild = [1,-1,3,-1], rightChild = [2,3,-1,-1]
Output: false
Example 3:

Input: n = 2, leftChild = [1,0], rightChild = [-1,-1]
Output: false
Example 4:

Input: n = 6, leftChild = [1,-1,-1,4,-1,-1], rightChild = [2,-1,-1,5,-1,-1]
Output: false
Constraints:
1 <= n <= 10^4
leftChild.length == rightChild.length == n
-1 <= leftChild[i], rightChild[i] <= n - 1
class Solution {
public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
int[] parent = new int[n];
for (int i = 0; i < n; i++)
parent[i] = i;
for (int i = 0; i < n; i++) {
// Things taken care of: Cycles
if (leftChild[i] != -1)
if (union(parent, i, leftChild[i]))
return false;
if (rightChild[i] != -1)
if (union(parent, i, rightChild[i]))
return false;
}
// For taking care of multiple heads
int count = 0;
for (int i = 0; i < n; i++)
if (parent[i] == i)
count++;
return count == 1;
}
public boolean union(int[] parent, int node1, int node2) {
int p1 = find(parent, node1);
int p2 = find(parent, node2);
if (p1 == p2)
return true;
parent[p1] = p2;
return false;
}
public int find(int[] parent, int node) {
if (node != parent[node])
parent[node] = find(parent, parent[node]);
return parent[node];
}
}
Last updated