From 59892b65a9810044ca7f135e39c8d44094224c85 Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Wed, 4 Dec 2024 08:07:57 +0100
Subject: Day 4 2024

---
 2024/04/day04a.cpp | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 2024/04/day04a.cpp

(limited to '2024/04/day04a.cpp')

diff --git a/2024/04/day04a.cpp b/2024/04/day04a.cpp
new file mode 100644
index 0000000..887ebef
--- /dev/null
+++ b/2024/04/day04a.cpp
@@ -0,0 +1,96 @@
+#include <algorithm>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+enum class Direction { U, D, R, L, UR, UL, DR, DL };
+Direction all_directions[] = {
+	Direction::U, Direction::D, Direction::R, Direction::L,
+	Direction::UR, Direction::UL, Direction::DR, Direction::DL
+};
+
+pair<int, int> step(pair<int, int> p, Direction d) {
+	auto [i, j] = p;
+
+	switch (d) {
+	case Direction::U:
+		return make_pair(i-1, j);
+	case Direction::D:
+		return make_pair(i+1, j);
+	case Direction::R:
+		return make_pair(i, j+1);
+	case Direction::L:
+		return make_pair(i, j-1);
+	case Direction::UR:
+		return make_pair(i-1, j+1);
+	case Direction::UL:
+		return make_pair(i-1, j-1);
+	case Direction::DR:
+		return make_pair(i+1, j+1);
+	case Direction::DL:
+		return make_pair(i+1, j-1);
+	}
+
+	return make_pair(-999,-999);
+}
+
+class Board {
+public:
+	int M, N;
+
+	Board(vector<string> &lines) {
+		N = lines.size();
+		M = 0;
+		for (string l : lines)
+			M = max(M, (int)l.size());
+		cells = new char[M * N];
+		for (int i = 0; i < N; i++)
+			for (int j = 0; j < M; j++)
+				cells[N*i + j] = j < (int)lines[i].size() ?
+				    lines[i][j] : out_of_bound;
+	}
+
+	string word_at(int i, int j, Direction d, int l) {
+		string ret = "";
+		auto p = make_pair(i, j);
+		for (int k = 0; k < l; k++, p = step(p, d))
+			ret += (*this)[p];
+		return ret;
+	}
+
+	~Board() {
+		delete []cells;
+	}
+
+private:
+	const char out_of_bound = '.';
+	char *cells;
+
+	char operator[](pair<int, int> p) {
+		auto [i, j] = p;
+		if (i >= N || i < 0 || j >= M || j < 0)
+			return out_of_bound;
+		return cells[N*i + j];
+	}
+};
+
+int main() {
+	string line;
+	vector<string> lines;
+	while (getline(cin, line))
+		lines.push_back(line);
+
+	Board board(lines);
+	int tot = 0;
+	for (int i = 0; i < board.N; i++)
+		for (int j = 0; j < board.M; j++)
+			for (Direction d : all_directions)
+				if (board.word_at(i, j, d, 4) == "XMAS")
+					tot++;
+	cout << tot << endl;
+
+	return 0;
+}
-- 
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