Create binary-trees-with-factors.cpp

Author: kamyu104

C++/binary-trees-with-factors.cpp

@@ -0,0 +1,23 @@
+// Time:  O(n^2)
+// Space: O(n)
+
+class Solution {
+public:
+    int numFactoredBinaryTrees(vector<int>& A) {
+        static const int M = 1e9 + 7;
+        sort(A.begin(), A.end());
+        unordered_map<int, int64_t> dp;
+        for (int i = 0; i < A.size(); ++i) {
+            dp[A[i]] = 1;
+            for (int j = 0; j < i; ++j) {
+                if (A[i] % A[j] == 0 && dp.count(A[i] / A[j])) {
+                   dp[A[i]] = (dp[A[i]] + dp[A[j]] * dp[A[i] / A[j]]) % M;
+                }
+            }
+        }
+        return accumulate(dp.cbegin(), dp.cend(), 0L,
+                          [](int64_t x, const pair<int, int>& p) {
+                              return x + p.second;
+                          }) % M;
+    }
+};