add 2024 day 2

2024/02.cpp

@@ -0,0 +1,77 @@
+#include <fstream>
+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+
+vector<int> parse_line(string line) {
+    int start = 0;
+    vector<int> result;
+    while (start < line.length()) {
+        int end = line.find(" ", start);
+
+        string word = line.substr(start, end - start);
+        int n = stoi(word);
+        result.push_back(n);
+
+        start = end + 1;
+        if (end == -1) {
+            break;
+        }
+    }
+
+    return result;
+}
+
+
+bool is_valid(vector<int> report) {
+    int prev_diff = 0;
+    for (int i = 1; i < report.size(); i++) {
+        int diff = report[i] - report[i - 1];
+        if (diff < -3 || diff == 0 || diff > 3) {
+            return false;
+        }
+
+        // on the first iteration, we can't compare to the previous difference
+        if (i == 1) {
+            prev_diff = diff;
+            continue;
+        }
+
+        if ((diff > 0 && prev_diff < 0) || (diff < 0 && prev_diff > 0)) {
+            return false;
+        }
+        prev_diff = diff;
+    }
+    return true;
+}
+
+
+int main() {
+    ifstream file("data/02.txt");
+    string line;
+    int count_part1 = 0;
+    int count_part2 = 0;
+    while (getline(file, line)) {
+        auto report = parse_line(line);
+        if (is_valid(report)) {
+            count_part1++;
+            count_part2++;
+        }
+        else {
+            for (int i = 0; i < report.size(); i++) {
+                int n = report[i];
+                report.erase(report.begin() + i);
+                if (is_valid(report)) {
+                    count_part2++;
+                    break;
+                }
+                report.insert(report.begin() + i, n);
+            }
+        }
+    }
+    cout << "Part 1: " << count_part1 << "\n";
+    cout << "Part 2: " << count_part2 << "\n";
+}