Create 1530. Number of Good Leaf Nodes Pairs (#533)

Author: Chayandas07

1530. Number of Good Leaf Nodes Pairs

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+class Solution {
+private:
+    int count = 0;
+    const int MAX_DISTANCE = 10;
+
+    vector<int> dfs(TreeNode* node, int distance) {
+        if (!node) return vector<int>(MAX_DISTANCE + 1, 0);
+        
+        if (!node->left && !node->right) {
+            vector<int> res(MAX_DISTANCE + 1, 0);
+            res[1] = 1;
+            return res;
+        }
+        
+        vector<int> left = dfs(node->left, distance);
+        vector<int> right = dfs(node->right, distance);
+        
+        for (int i = 1; i <= distance; i++) {
+            for (int j = 1; j <= distance - i; j++) {
+                count += left[i] * right[j];
+            }
+        }
+        
+        vector<int> res(MAX_DISTANCE + 1, 0);
+        for (int i = 1; i < MAX_DISTANCE; i++) {
+            res[i + 1] = left[i] + right[i];
+        }
+        
+        return res;
+    }
+
+public:
+    int countPairs(TreeNode* root, int distance) {
+        dfs(root, distance);
+        return count;
+    }
+};