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LeetCode-Count Univalue Subtrees
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,
5 / 1 5 / \ 5 5 5
return 4.
Solution:
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */public class Solution { public class UniValueCount { int value; boolean isUniValue; int count; public UniValueCount(int v, boolean is, int num){ value = v; isUniValue = is; count = num; } } public int countUnivalSubtrees(TreeNode root) { UniValueCount res = countUnivalRecur(root); return res.count; } public UniValueCount countUnivalRecur(TreeNode cur){ if (cur==null){ return new UniValueCount(0,false,0); } if (cur.left==null && cur.right==null){ return new UniValueCount(cur.val,true,1); } UniValueCount res = new UniValueCount(0,true,0); if (cur.left!=null){ UniValueCount leftRes = countUnivalRecur(cur.left); res.isUniValue = res.isUniValue && (leftRes.isUniValue && cur.val==leftRes.value); res.count += leftRes.count; } if (cur.right!=null){ UniValueCount rightRes = countUnivalRecur(cur.right); res.isUniValue = res.isUniValue && (rightRes.isUniValue && cur.val==rightRes.value); res.count += rightRes.count; } if (res.isUniValue){ res.count++; res.value = cur.val; } return res; }}
LeetCode-Count Univalue Subtrees
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