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.
For example:
Given binary tree,
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| 5
/ \
1 5
/ \ \
5 5 5
|
return 4.
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| public class CountUnivalueSubtrees {
public int countUnivalSubtrees(TreeNode root) {
if (root == null) {
return 0;
}
if (root.left == null && root.right == null) {
return 1;
}
int[] result = new int[]{0};
helper(root, result);
return result[0];
}
private boolean helper(TreeNode root, int[] result) {
if (root.right == null && root.left == null) {
result[0]++;
return true;
} else if (root.right != null && root.left == null) {
if (helper(root.right, result) && root.val == root.right.val) {
result[0]++;
return true;
} else {
return false;
}
} else if (root.right == null) {
if (helper(root.left, result) && root.val == root.left.val) {
result[0]++;
return true;
} else {
return false;
}
} else {
boolean l = helper(root.right, result);
boolean r = helper(root.left, result);
if (l && r && root.val == root.left.val && root.val == root.right.val) {
result[0]++;
return true;
} else {
return false;
}
}
}
}
|