Added older advents

advent_of_code_2015/day2/main1.cc

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+#include <iostream>
+#include <string>
+
+using namespace std;
+
+struct Present
+{
+    size_t length;
+    size_t width;
+    size_t height;
+
+    size_t extra_wrap()
+    {
+        return min(length * width, min(length * height, width * height));
+    }
+
+    size_t wrap_required()
+    {
+        return 2 * length * width
+            + 2 * width * height
+            + 2 * height * length
+            + extra_wrap();
+    }
+
+    size_t bow_size()
+    {
+        return length * width * height;
+    }
+
+    size_t ribbon_required()
+    {
+        size_t ribbon = min(length + width, min(length + height, width + height)) * 2;
+        return ribbon + bow_size();
+    }
+};
+
+istream &operator>>(istream& in, Present &present)
+{
+    in >> present.length;
+    in.ignore(1); // ignore 'x'.
+    in >> present.width;
+    in.ignore(1); // ignore 'x'.
+    in >> present.height;
+
+    return in;
+}
+
+int main()
+{
+    size_t total_wrap = 0;
+    size_t total_ribbon = 0;
+    Present present;
+
+    while(!cin.eof())
+    {
+        cin >> present;
+        total_wrap += present.wrap_required();
+        total_ribbon += present.ribbon_required();
+    }
+
+    cout << "Total wrap required: " << total_wrap << "\n";
+    cout << "Total ribbon required: " << total_ribbon << "\n";
+}