Create factor-combinations.cpp

Author: kamyu104

C++/factor-combinations.cpp

@@ -0,0 +1,26 @@
+// Time:  O(nlogn) = logn * n^(1/2) * n^(1/4) * ... * 1
+// Space: O(logn)
+
+// DFS solution.
+class Solution {
+    public:
+        vector<vector<int>> getFactors(int n) {
+            vector<vector<int>> result;
+            vector<int> factors;
+            getResult(n, &result, &factors);
+            return result;
+        }
+
+        void getResult(const int n, vector<vector<int>> *result, vector<int> *factors) {
+            for (int i = factors->empty() ? 2 : factors->back(); i <= n / i; ++i) {
+                if (n % i == 0) {
+                    factors->emplace_back(i);
+                    factors->emplace_back(n / i);
+                    result->emplace_back(*factors);
+                    factors->pop_back();
+                    getResult(n / i, result, factors);
+                    factors->pop_back();
+                }
+            }
+        }
+    };