subTree.java

import java.util.ArrayDeque;
import java.util.Queue;



public class subTree {
    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 boolean isSubtree(TreeNode s, TreeNode t) {
    Queue<TreeNode> nodes = new ArrayDeque<>();
    nodes.offer(s);
    while (!nodes.isEmpty()) {
        TreeNode node = nodes.poll();
        if (isSameTree(node, t)) {
            return true;
        }
        if (node.left != null) {
            nodes.offer(node.left);
        }
        if (node.right != null) {
            nodes.offer(node.right);
        }
    }
    return false;
}

public boolean isSameTree(TreeNode s, TreeNode t) {
    if (s == null && t == null) {
        return true;
    }
    if (s == null || t == null) {
        return false;
    }
    if (s.val != t.val) {
        return false;
    } else {
        return isSameTree(s.left, t.left) && isSameTree(s.right, t.right);
    }
}

}