Day 4 (sorry I am late) Question 1

Day4/Question1/main.cpp

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+#include <algorithm>
+#include <cstdint>
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <string>
+
+#define POSITON_TO_INDEX(x, y) (y * width) + x
+#define SEARCHBOX_WIDTH 3
+#define SEARCHBOX_HEIGTH 3
+
+// Basically floor(SEARCHBOX_WIDTH/2)
+#define SEARCHBOX_HALF 1
+
+int main() {
+  std::ifstream input("input");
+  std::string wholeFile(std::istreambuf_iterator<char>{input}, {});
+
+  uint16_t width, height, length;
+  width = wholeFile.find('\n');
+
+  // Note for self, std::remove is an algorithm that gets a range and then
+  // removes a specific value, however it returns a forward iterator, not the
+  // type itself. Neat thing with the iterator is that you can use
+  // std::string::erase with it to basically presicion strike specific
+  // characters from an existing string. Iterated value must be same as the
+  // array(std::string = std::basic_string<char>, hence must use char)
+  wholeFile.erase(std::remove(wholeFile.begin(), wholeFile.end(), '\n'),
+                  wholeFile.end());
+
+  // Need \n for width, for rest it screws with the result
+  length = wholeFile.length();
+  height = length / width;
+
+  // Range
+  // x = 0 <= currentPosition < width
+  // y = 0 <= currentPosition < height
+  char currentCharacter = ' ';
+  uint16_t x = 0, y = 0, totalAvailable = 0;
+  for (uint16_t currentPosition = 0; currentPosition < length;
+       currentPosition++) {
+    currentCharacter = wholeFile.at(currentPosition);
+    if (currentCharacter != '@') {
+      continue;
+    }
+
+    // Really convenient that integers are floored
+    x = currentPosition % width;
+    y = currentPosition / height;
+    uint8_t neighbourCount = 0;
+
+    // Just check for 5 since we know middle is definetly @ always
+    for (int16_t index = 0, widthCounter = SEARCHBOX_HALF * -2,
+                 currentGlobalIndex = 0, currentX = 0, currentY = 0;
+         index < SEARCHBOX_WIDTH * SEARCHBOX_HEIGTH; index++) {
+      if (neighbourCount == 5) {
+        break;
+      }
+
+      if (index % SEARCHBOX_WIDTH == 0) {
+        widthCounter++;
+      }
+
+      // Edge case, corners don't wrap
+      currentX = (x - SEARCHBOX_HALF) + index % SEARCHBOX_WIDTH;
+      currentY = y + widthCounter;
+
+      if (currentX < 0 || currentX >= width || currentY < 0 ||
+          currentY >= height) {
+        continue;
+      }
+
+      // Make sure index is valid
+      currentGlobalIndex = POSITON_TO_INDEX(currentX, currentY);
+
+      if (wholeFile.at(currentGlobalIndex) == '@') {
+        neighbourCount++;
+      }
+    }
+
+    totalAvailable += neighbourCount < 5;
+  }
+  std::cout << totalAvailable << std::endl;
+
+  return 0;
+}