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.
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.
/**
* Definition for a binary tree node.
* public class TreeNode {
* public int val;
* public TreeNode left;
* public TreeNode right;
* public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
public class Solution {
public bool IsSubtree(TreeNode s, TreeNode t) {
if(t==null){
return true;
}
if(s==null && t!=null){
return false;
}
if(s.val==t.val){
if(IsEqual(s.left,t.left) && IsEqual(s.right,t.right)){
return true;
}
}
return IsSubtree(s.left,t) || IsSubtree(s.right,t);
}
private bool IsEqual(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;
}
return IsEqual(s.left,t.left) && IsEqual(s.right,t.right);
}
}
Time Complexity: O(2^n)
Space Complexity: O(1)