Sync LeetCode submission Runtime - 3 ms (97.01%), Memory - 25.1 MB (41.18%)

Author: koralkulacoglu

LeetCode/0508-most-frequent-subtree-sum/README.md

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+<p>Given the <code>root</code> of a binary tree, return the most frequent <strong>subtree sum</strong>. If there is a tie, return all the values with the highest frequency in any order.</p>
+
+<p>The <strong>subtree sum</strong> of a node is defined as the sum of all the node values formed by the subtree rooted at that node (including the node itself).</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/04/24/freq1-tree.jpg" style="width: 207px; height: 183px;" />
+<pre>
+<strong>Input:</strong> root = [5,2,-3]
+<strong>Output:</strong> [2,-3,4]
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/04/24/freq2-tree.jpg" style="width: 207px; height: 183px;" />
+<pre>
+<strong>Input:</strong> root = [5,2,-5]
+<strong>Output:</strong> [2]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the tree is in the range <code>[1, 10<sup>4</sup>]</code>.</li>
+	<li><code>-10<sup>5</sup> &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
+</ul>

LeetCode/0508-most-frequent-subtree-sum/solution.cpp

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+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    int mostFreq;
+    unordered_map<int, int> freq;
+    
+    int dfs(TreeNode* root) {
+        if (root == nullptr) return 0;
+
+        int leftSum = dfs(root->left);
+        int rightSum = dfs(root->right);
+        int sum = root->val + leftSum + rightSum;
+
+        freq[sum]++;
+        mostFreq = max(mostFreq, freq[sum]);
+
+        return sum;
+    }
+
+public:
+    vector<int> findFrequentTreeSum(TreeNode* root) {
+        mostFreq = 0;
+        dfs(root);
+
+        vector<int> res;
+        for (auto i : freq) {
+            if (i.second == mostFreq) res.push_back(i.first);
+        }
+
+        return res;
+    }
+};
+