Description
Given a binary tree, count the number of uni-value subtrees.
A Uni-value subtree means all nodes of the subtree have the same value.
Example
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| Input: root = [5,1,5,5,5,null,5]
5
/ \
1 5
/ \ \
5 5 5
Output: 4
|
Solution
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class Solution {
int res = 0;
public int countUnivalSubtrees(TreeNode root) {
if (root == null) return 0;
helper(root);
return res;
}
private boolean helper(TreeNode root){
if (root == null) return true;
if (root.left == null && root.right == null){
res++;
return true;
}
boolean left = helper(root.left);
boolean right = helper(root.right);
if (!left || !right) return false;
if (root.left == null){
if (root.val == root.right.val){
res++;
return true;
}
}
else if (root.right == null){
if (root.val == root.left.val){
res++;
return true;
}
}
else{
if (root.val == root.left.val && root.val == root.right.val){
res++;
return true;
}
}
return false;
}
}
|