Add solution for 2015 Day 20

res/2015/day20/test_input.txt

@@ -0,0 +1 @@
+149

src/2015/Day20.cpp

@@ -2,30 +2,51 @@
 
 namespace y2015::day20
 {
-  REGISTER_DAY(2015, Day20, std::vector<int>, int);
+  REGISTER_DAY(2015, Day20, int, int);
 
-  REGISTER_TEST_EXAMPLE(2015, Day20, ExampleInput, 1, 0);
-  REGISTER_TEST(2015, Day20, Input, 1, 0);
-  REGISTER_TEST_EXAMPLE(2015, Day20, ExampleInput, 2, 0);
-  REGISTER_TEST(2015, Day20, Input, 2, 0);
+  REGISTER_TEST_EXAMPLE(2015, Day20, ExampleInput, 1, 8);
+  REGISTER_TEST(2015, Day20, Input, 1, 776160);
+  REGISTER_TEST_EXAMPLE(2015, Day20, ExampleInput, 2, 8);
+  REGISTER_TEST(2015, Day20, Input, 2, 786240);
 
   READ_INPUT(input)
   {
-    std::vector<int> vec;
-    std::string str;
-    while (getline(input, str))
+    int i = 0;
+    input >> i;
+    return i;
+  }
+
+  int Solve(int input, int visits, int gifts)
+  {
+    // Assumption is that the solution can be found in 'limit' amount houses
+    int limit = 1'000'000;
+    if (visits == -1)
+      visits = limit;
+    std::vector<int> data(limit, 0);
+    for (int i = 1; i < limit; i++)
     {
+      for (int j = 1; j <= visits; j++)
+      {
+        if (i * j - 1 >= limit)
+          break;
+        data[i * j - 1] += i * gifts;
+      }
     }
-    return vec;
+    for (int i = 0; i < data.size(); i++)
+    {
+      if (data[i] > input)
+        return i + 1;
+    }
+    return 0;
   }
 
   OUTPUT1(input)
   {
-    return 0;
+    return Solve(input, -1, 10);
   }
 
   OUTPUT2(input)
   {
-    return 0;
+    return Solve(input, 50, 11);
   }
 }