solve(day 4): Ceres search part 1

day-3/01.cpp

@@ -2,12 +2,12 @@
 
 using namespace std;
 
-int computeMuls(const string& line) {
+int computeFlaggedMuls(const string& line) {
     int subComputation = 0;
 
     // We're going to read the substring of each (idx, idx+4) to match a
     // `mult(` sequence
-    for (size_t i = 0; i+4 <= line.size(); i++) {
+    for (size_t i = 0; i + 4 <= line.size(); i++) {
         if (line.substr(i, 4) == "mul(") {
             int a = 0;
             int b = 0;
@@ -21,7 +21,7 @@ int computeMuls(const string& line) {
 
                 // Edge case: must be closed by a ')' character
                 if (ch != ')') continue;
-                
+
                 subComputation += a * b;
             }
         }
@@ -50,11 +50,11 @@ int main() {
 
     // The input is a long string where each line contains some `mul(a,b)`
     // instructions
-    string line;
+    string token;
     int computation = 0;
 
-    while (inputFile >> line) {
-        computation += computeMuls(line);
+    while (inputFile >> token) {
+        computation += computeFlaggedMuls(token);
     }
 
     cout << "computed: " << computation << '\n';

day-3/02.cpp

@@ -0,0 +1,80 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int computeFlaggedMuls(const string& line) {
+    bool isEnabled = true;
+    int subComputation = 0;
+
+    // We're going to read the substring of each (idx, idx+4) to match a
+    // `mult(` sequence
+    for (size_t i = 0; i + 4 <= line.size(); i++) {
+        // Scan the line for do() / don't() sequences
+        if (line.substr(i, 4) == "do()") {
+            cout << "'do' detected at idx: " << i << '\n';
+            isEnabled = true;
+            i += 3;
+            continue;
+        }
+
+        if (i + 7 <= line.size() && line.substr(i, 7) == "don't()") {
+            cout << "'do' detected at idx: " << i << '\n';
+            isEnabled = false;
+            i += 6;
+            continue;
+        }
+
+        cout << "enabled: " << isEnabled << '\n';
+
+        if (line.substr(i, 4) == "mul(") {
+            int a = 0;
+            int b = 0;
+
+            // If we can scan out an offset of the line with two integers,
+            // attempt to compute it
+            if (sscanf(line.c_str() + i, "mul(%d,%d)", &a, &b) == 2) {
+                char ch;
+
+                sscanf(line.c_str() + i, "mul(%d,%d%c", &a, &b, &ch);
+
+                if (ch != ')') continue;
+
+                if (isEnabled) subComputation += a * b;
+            }
+        }
+    }
+
+    // This is the result of the mul() computations for this line
+    return subComputation;
+}
+
+int main() {
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+
+    cout << "Input File: ";
+    string filename;
+
+    cout.flush();
+    getline(cin, filename);
+
+    ifstream inputFile("day-3/" + filename);
+
+    if (!inputFile.is_open()) {
+        cerr << "Unable to open this file.\n";
+        return 1;
+    }
+
+    // The input is a long string where each line contains some `mul(a,b)`
+    // instructions
+    string line;
+    int computation = 0;
+
+    while (getline(inputFile, line)) {
+        computation += computeFlaggedMuls(line);
+    }
+
+    cout << "computed flagged muls: " << computation << '\n';
+
+    return 0;
+}

day-4/01.cpp

@@ -0,0 +1,75 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int rowDir[] = {0, 1, 0, -1, 1, 1, -1, -1};
+int colDir[] = {1, 0, -1, 0, 1, -1, 1, -1};
+
+bool isSafe(int x, int y, int rows, int cols) {
+    return x >= 0 && x < rows && y >= 0 && y < cols;
+}
+
+int countXMAS(const vector<string>& grid, const string& word = "XMAS") {
+    int rows = grid.size();
+    int cols = grid[0].size();
+    int wordLen = word.size();
+    int count = 0;
+
+    for (int i = 0; i < rows; ++i) {
+        for (int j = 0; j < cols; ++j) {
+            if (grid[i][j] == word[0]) {
+                // Check all 8 directions
+                for (int dir = 0; dir < 8; ++dir) {
+                    int x = i, y = j;
+                    bool found = true;
+
+                    for (int k = 1; k < wordLen; ++k) {
+                        x += rowDir[dir];
+                        y += colDir[dir];
+
+                        if (!isSafe(x, y, rows, cols) ||
+                            grid[x][y] != word[k]) {
+                            found = false;
+                            break;
+                        }
+                    }
+
+                    if (found) {
+                        ++count;
+                    }
+                }
+            }
+        }
+    }
+
+    return count;
+}
+
+int main() {
+    ios::sync_with_stdio(0);
+    cin.tie(nullptr);
+
+    string filename;
+    cout << "Input file: ";
+    cout.flush();
+
+    getline(cin, filename);
+
+    ifstream inputFile("day-4/" + filename);
+    if (!inputFile.is_open()) {
+        cerr << "Unable to read input file.";
+        return 1;
+    }
+
+    vector<string> grid = {};
+    string line;
+
+    while (getline(inputFile, line)) {
+        grid.push_back(line);
+    }
+
+    int result = countXMAS(grid);
+    cout << "XMAS count: " << result << '\n';
+
+    return 0;
+}