solve(day 1): Historian hysteria part 1

.gitignore

@@ -0,0 +1 @@
+runfile

01/01.cpp

@@ -0,0 +1,50 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+typedef long long ll;
+typedef vector<ll> vecLL;
+
+int main() {
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+
+    ll l1 = 0;
+    ll l2 = 0;
+
+    vecLL list1 = {};
+    vecLL list2 = {};
+
+    // Read input file
+    ifstream inputFile("./01/input.txt");
+
+    if (!inputFile.is_open()) {
+        cerr << "Error: Could not open file.\n";
+        return 1;
+    }
+
+    // Build both lists from input
+    while (inputFile >> l1 >> l2) {
+        cout << "l1: " << l1 << " l2: " << l2 << '\n';
+        list1.push_back(l1);
+        list2.push_back(l2);
+    }
+
+    // Close file (free memory)
+    inputFile.close();
+
+    // Sort both lists
+    sort(list1.begin(), list1.end());
+    sort(list2.begin(), list2.end());
+
+    // Compare each element and sum absolute diff (both lists are same size)
+    ll diff = 0;
+
+    for (size_t i = 0; i < list1.size(); i++) {
+        diff += abs(list1[i] - list2[i]);
+    }
+
+    cout << "diff: " << diff << '\n';
+
+    return 0;
+}