0572-subtree-of-another-tree

572. Subtree of Another Tree

Problem Description

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considered as a subtree of itself.

Detail instruction can be found here.

Example 1:

Given tree s:

     3
    / \
   4   5
  / \
 1   2
Given tree t:
   4 
  / \
 1   2
Return true, because t has the same structure and node values with a subtree of s.

Example 2:

Given tree s:

     3
    / \
   4   5
  / \
 1   2
    /
   0
Given tree t:
   4
  / \
 1   2
Return false.

Solution

Approach 1: Recursive

private boolean isIdentical(TreeNode s, TreeNode t) {
    if (s == null && t == null)
        return true;
    if (s == null || t == null)
        return false;
    
    return (s.val == t.val) && isIdentical(s.left, t.left) && isIdentical(s.right, t.right);
}
public boolean isSubtree(TreeNode s, TreeNode t) {
    if (s == null) return false;
    return isIdentical(s, t) || isSubtree(s.left, t) || isSubtree(s.right, t);
}

Approach 2: Iterative

// TODO

Definition for a Node

public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

Test

Compile with javac Solution.java and run with java Solution.

This is only for discussion and communication. Please don't use this for submission of assignments.