CodingProblems/CountUniValueSubtree.java at master · PerrySong/CodingProblems · GitHub

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importjava.util.HashMap;
importjava.util.LinkedList;
importjava.util.Map;
importjava.util.Queue;

publicclassCountUniValueSubtree {

/**
 *
 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 :

 Input: root = [5,1,5,5,5,null,5]

 5
 / \
 1 5
 / \ \
 5 5 5

 Output: 4
 */

publicintcountUnivalSubtrees(TreeNoderoot) {
if(root == null) return0;
int[] res = newint[]{0};
Map<TreeNode, Boolean> map = newHashMap<>();
isUnival(root, map, res);

returnres[0];
 }

publicbooleanisUnival(TreeNoderoot, Map<TreeNode, Boolean> map, int[] res) {
if(root == null) returntrue;
if(map.get(root) != null) returnmap.get(root);
booleanleft = isUnival(root.left, map, res);
booleanright = isUnival(root.right, map, res);

if(left && right) {
if(root.left != null && root.left.val != root.val) {
map.put(root, false);
returnfalse;
 } if(root.right != null && root.right.val != root.val) {
map.put(root, false);
returnfalse;
 } else {
res[0]++;
map.put(root, true);
returntrue;
 }

 }
returnfalse;
 }
}