Day 9 2024

3 files changed, 102 insertions, 0 deletions

diff --git a/2024/09/Makefile b/2024/09/Makefile
new file mode 100644
index 0000000..89cd1b9
--- /dev/null
+++ b/2024/09/Makefile
@@ -0,0 +1,24 @@
+CC=g++ -std=c++20 -g -Wall
+
+a:
+        ${CC} -o a.out day09a.cpp
+
+b:
+        ${CC} -o b.out day09b.cpp
+
+clean:
+        rm -f a b
+
+atest: a
+        ./a.out
+
+btest: b
+        ./b.out
+
+arun: a
+        ./a.out < input
+
+brun: b
+        ./b.out < input
+
+.PHONY: a b clean atest btest arun brun
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;
+}
diff --git a/2024/09/day09b.cpp b/2024/09/day09b.cpp
new file mode 100644
index 0000000..3b1ac21
--- /dev/null
+++ b/2024/09/day09b.cpp
@@ -0,0 +1,46 @@
+#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;
+        vector<pair<int, int>> freesp, file;
+        char c;
+        for (int id = 0; cin >> c; id++) {
+                if (id % 2 == 1)
+                        freesp.push_back(make_pair(a.size(), c-'0'));
+                else
+                        file.push_back(make_pair(a.size(), c-'0'));
+                for (int j = 0; j < c-'0'; j++)
+                        a.push_back(id % 2 == 0 ? id/2 : -1); // -1 = space
+        }
+
+        for (int i = file.size()-1; i >= 0; i--) {
+                for (auto& f : freesp) {
+                        if (f.first >= file[i].first) break;
+                        if (f.second >= file[i].second) {
+                                for (int k = 0; k < file[i].second; k++) {
+                                        a[f.first+k] = a[file[i].first+k];
+                                        a[file[i].first+k] = -2;
+                                }
+                                f.first += file[i].second;
+                                f.second -= file[i].second;
+                                break;
+                        }
+                }
+        }
+
+        long long checksum = 0;
+        for (long long i = 0; i < (long long)a.size(); i++)
+                if (a[i] >= 0)
+                        checksum += i*a[i];
+        cout << checksum << endl;
+
+        return 0;
+}