From 93f9d02e978d10b4ff02ac029b6a6eff3d3193cf Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Mon, 9 Dec 2024 06:36:25 +0100
Subject: Day 9 2024

---
 2024/09/day09a.cpp | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 2024/09/day09a.cpp

(limited to '2024/09/day09a.cpp')

diff --git a/2024/09/day09a.cpp b/2024/09/day09a.cpp
new file mode 100644
index 0000000..c52c8f0
--- /dev/null
+++ b/2024/09/day09a.cpp
@@ -0,0 +1,32 @@
+#include <algorithm>
+#include <iostream>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+int main() {
+	vector<long long> a;
+	char c;
+	for (int id = 0; cin >> c; id++)
+		for (int j = 0; j < c-'0'; j++)
+			a.push_back(id % 2 == 0 ? id/2 : -1); // -1 = space
+
+	int j = 0;
+	for (int i = a.size()-1; i >= 0; i--) {
+		while (a[j] >= 0) j++;
+		if (a[j] == -2) break;
+		a[j] = a[i];
+		a[i] = -2; // -2 = freed up
+	}
+
+	long long checksum = 0;
+	for (long long i = 0; i < (long long)a.size() && a[i] != -2; i++)
+		checksum += i*a[i];
+	cout << checksum << endl;
+
+	return 0;
+}
-- 
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