/*

This code has been written by - Amrit Raj

This is a functional code with the following specifications:-

Arguments - Root node of the Tree defined by class TreeNode

Return - An int signifying the second minimum node in the given tree. In case

it is not found, it returns -1

*/

public int findSecondMinimumValue(TreeNode root) {

//A queue to store the nodes..

Queue<TreeNode> q = new ArrayDeque<>();

if (root == null)

return -1;

int min = root.val;

int secondMin = Integer.MAX_VALUE;

boolean found = false;

q.add(root);

while (!q.isEmpty()) {

int size = q.size();

for (int i = 0; i < size; i++) {

TreeNode node = q.poll();

if (node.val > min) {

secondMin = Math.min(node.val, secondMin);

found = true;

continue;

}

//Left subtree..

if (node.left != null && node.left.val <= secondMin)

q.add(node.left);

//Right Subtree

if (node.right != null && node.right.val <= secondMin)

q.add(node.right);

}

}

//Returning second min, else -1...

return found? secondMin : -1;

}