advent2024

commit 9c1579e5f46c278778821ab129deec7fe342e94f
parent 0ec0bb8327ec020333db58355dc500d3dd8c4b26
Author: bsandro <email@bsandro.tech>
Date:   Fri, 27 Dec 2024 00:40:00 +0200

Day 13 p2

Diffstat:
M
day13/Makefile
 | 
4
++--
M
day13/main.cpp
 | 
45
++++++++++++++++++++++++++++++++-------------

2 files changed, 34 insertions(+), 15 deletions(-)
diff --git a/day13/Makefile b/day13/Makefile
@@ -3,9 +3,9 @@ UNAME_S:=$(shell uname -s)
 SRC:=$(wildcard *.cpp)
 DEPS:=$(wildcard *.hpp)
 OBJ:=$(SRC:.cpp=.o)
-CXXSTD:="c++23"
+CXXSTD:=c++23
 ifeq (${UNAME_S},OpenBSD)
-CXXSTD="c++2b"
+CXXSTD=c++2b
 endif
 $(info advent of code on ${UNAME_S})
 CXXFLAGS=-O2 -std=${CXXSTD} -Werror -Wall -Wextra -I. -I../include
diff --git a/day13/main.cpp b/day13/main.cpp
@@ -10,11 +10,17 @@
 #include "utils.hpp"
 
 struct Vec2 {
-    int x;
-    int y;
+    int64_t x;
+    int64_t y;
     void fromStr(const std::string &s) {
         [[ maybe_unused ]] char btn;
-        std::sscanf(s.c_str(), "Button %c: X+%d, Y+%d", &btn, &x, &y);
+        std::sscanf(s.c_str(), "Button %c: X+%lld, Y+%lld", &btn, &x, &y);
+    }
+    bool operator==(const Vec2 &other) const {
+        return this->x==other.x && this->y==other.y;
+    }
+    bool operator!=(const Vec2 &other) const {
+        return this->x!=other.x || this->y!=other.y;
     }
 };
 
@@ -23,10 +29,10 @@ struct Machine {
     Vec2 btnB;
     Vec2 prize;
     void setPrize(const std::string &s) {
-        std::sscanf(s.c_str(), "Prize: X=%d, Y=%d", &prize.x, &prize.y);
+        std::sscanf(s.c_str(), "Prize: X=%lld, Y=%lld", &prize.x, &prize.y);
     }
     void print() const {
-        std::printf("A(%d,%d), B(%d,%d), prize at (%d,%d)\n", btnA.x, btnA.y, btnB.x, btnB.y, prize.x, prize.y);
+        std::printf("A(%lld,%lld), B(%lld,%lld), prize at (%lld,%lld)\n", btnA.x, btnA.y, btnB.x, btnB.y, prize.x, prize.y);
     }
 };
 
@@ -65,9 +71,9 @@ T read_file(const std::string &path) {
     return buf;
 }
 
-bool simulate(const Machine &m, int pA, int pB, std::vector<int> &out) {
-    int curX = m.btnA.x*pA + m.btnB.x*pB;
-    int curY = m.btnA.y*pA + m.btnB.y*pB;
+bool simulate(const Machine &m, int64_t pA, int64_t pB, std::vector<int64_t> &out) {
+    int64_t curX = m.btnA.x*pA + m.btnB.x*pB;
+    int64_t curY = m.btnA.y*pA + m.btnB.y*pB;
     if (curX>m.prize.x||curY>m.prize.y) return false;
     if (curX==m.prize.x&&curY==m.prize.y) {
         out.push_back(pA*3+pB);
@@ -75,10 +81,10 @@ bool simulate(const Machine &m, int pA, int pB, std::vector<int> &out) {
     return true;
 }
 
-int64_t part1(Data &input [[ maybe_unused ]]) {
+int64_t part1(const Data &input [[ maybe_unused ]]) {
     int64_t res = 0;
     for (auto &m:input) {
-        std::vector<int> runs;
+        std::vector<int64_t> runs;
         for (int a=0;a<100;a++) {
             for (int b=0;b<100;b++) {
                 if (!simulate(m, a, b, runs)) break;
@@ -90,8 +96,22 @@ int64_t part1(Data &input [[ maybe_unused ]]) {
 
     return res;
 }
-int64_t part2(Data &input [[ maybe_unused ]]) {
-    return 0;
+
+int64_t part2(Data input [[ maybe_unused ]]) {
+    int64_t res = 0;
+    for (auto &m:input) {
+        m.prize.x += 10000000000000;
+        m.prize.y += 10000000000000;
+        int64_t pA = (m.prize.x*m.btnB.y-m.prize.y*m.btnB.x)/(m.btnA.x*m.btnB.y-m.btnA.y*m.btnB.x);
+        int64_t pB = (m.prize.y*m.btnA.x-m.prize.x*m.btnA.y)/(m.btnA.x*m.btnB.y-m.btnA.y*m.btnB.x);
+        Vec2 c;
+        c.x = m.btnA.x*pA + m.btnB.x*pB;
+        c.y = m.btnA.y*pA + m.btnB.y*pB;
+        if (c==m.prize) {
+            res += pA*3+pB;
+        }
+    }
+    return res;
 }
 
 int main(int argc, char **argv) {
@@ -101,6 +121,5 @@ int main(int argc, char **argv) {
     Data input = read_file<Data>(fname);
     std::cout << "part1: " << part1(input) << std::endl;
     std::cout << "part2: " << part2(input) << std::endl;
-
     return 0;
 }