1 files changed, 45 insertions, 0 deletions

diff --git a/2023/09/src/part2.cpp b/2023/09/src/part2.cpp
new file mode 100644
index 0000000..df1ec5a
--- /dev/null
+++ b/2023/09/src/part2.cpp
@@ -0,0 +1,45 @@
+#include <numeric>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <vector>
+
+void solve(std::vector<int> v, int& answer)
+{
+    for (int a = 0; a < v.size() - 1; ++a)
+    {
+        answer += v[a];
+        for (int b = v.size() - 1; b > a; --b)
+        {
+            v[b] = v[b-1] - v[b];
+        }
+    }
+}
+
+int main(int argc, char* argv[])
+{
+    int answer{};
+
+    std::ifstream input{ argv[1] };
+    if (input.is_open())
+    {
+        std::string line;
+        while (not std::getline(input,line).eof())
+        {
+            int n;
+            std::vector<int> v{};
+            std::istringstream sline{ line };
+            while(sline >> n)
+            {
+                v.push_back(n);
+            }
+
+            solve(std::move(v), answer);
+        }
+    }
+    input.close();
+
+    std::cout << answer << std::endl;
+    return 0;
+}
+