commit 59892b65a9810044ca7f135e39c8d44094224c85
parent 4aebede600c180b51d0b6ded0e42ec8a4223283e
Author: Sebastiano Tronto <sebastiano@tronto.net>
Date: Wed, 4 Dec 2024 08:07:57 +0100
Day 4 2024
Diffstat:
5 files changed, 236 insertions(+), 0 deletions(-)
diff --git a/2024/04/Makefile b/2024/04/Makefile
@@ -0,0 +1,24 @@
+CC=g++ -std=c++20 -g -Wall
+
+a:
+ ${CC} -o a.out day04a.cpp
+
+b:
+ ${CC} -o b.out day04b.cpp
+
+clean:
+ rm -f a b
+
+atest: a
+ ./a.out
+
+btest: b
+ ./b.out
+
+arun: a
+ ./a.out < input
+
+brun: b
+ ./b.out < input
+
+.PHONY: a b clean atest btest arun brun
diff --git a/2024/04/b.out b/2024/04/b.out
Binary files differ.
diff --git a/2024/04/day04a.cpp 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;
+}
diff --git a/2024/04/day04b.cpp b/2024/04/day04b.cpp
@@ -0,0 +1,114 @@
+#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++) {
+ int tmp = 0;
+ auto p = make_pair(i, j);
+ auto [x, y] = step(p, Direction::UL);
+ string wUL = board.word_at(x, y, Direction::DR, 3);
+ tmp += wUL == "MAS";
+
+ pair<int&, int&>(x, y) = step(p, Direction::UR);
+ string wUR = board.word_at(x, y, Direction::DL, 3);
+ tmp += wUR == "MAS";
+
+ pair<int&, int&>(x, y) = step(p, Direction::DL);
+ string wDL = board.word_at(x, y, Direction::UR, 3);
+ tmp += wDL == "MAS";
+
+ pair<int&, int&>(x, y) = step(p, Direction::DR);
+ string wDR = board.word_at(x, y, Direction::UL, 3);
+ tmp += wDR == "MAS";
+
+ if (tmp == 2) tot++;
+ }
+ }
+ cout << tot << endl;
+
+ return 0;
+}
diff --git a/2024/learned.txt b/2024/learned.txt
@@ -3,3 +3,5 @@ List of things I learned (or refreshed) with this year's AoC.
* Day 1: std::count()
* Day 2: std::sstream
* Day 3: std::string_view
+* Day 4: nothing special, some practice with classic and a weird trick
+ to assign two variables at once with a pair of references pair<int&, int&>
