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