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2DBussy shad/ban :!marseykneel::marseydeux::marseykneel:  2yr ago (text post) 398 thread views #129962

Advent of Code 2022 : Day 9

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In my part one, i just set the tail = previous position of head, if head and tail were >sqrt(2) away, took me way to long, to notice it


#include <iostream> 
#include <cmath>
#include <set>
#include <fstream>
#include <string>
#include <vector>
#include <numbers>

struct Point {
    int x = 0;
    int y = 0;

    auto operator<=>(const Point&) const = default;

    double inline distance(const Point& b) const {
        return std::sqrt(
            std::pow(x - b.x, 2) +
            std::pow(y - b.y, 2)
        );
    }

    Point calculate_move_vector(const Point& p) const {
        Point out;
        out.x = (p.x - x);
        out.y = (p.y - y);
        if(out.x != 0) out.x = out.x / std::abs(out.x);
        if(out.y != 0) out.y = out.y / std::abs(out.y);
        return out;
    }

    Point& operator+=(const Point& p) {
        this->x += p.x;
        this->y += p.y;
        return *this;
    }
};

struct Instruction {
    char direction;
    int moves;
};

void move(std::vector<Point>& knots, Instruction ins, std::set<Point>& v) {
    Point dir;
    if (ins.direction == 'R') dir = { 1, 0 };
    else if (ins.direction == 'U') dir = { 0, 1 };
    else if (ins.direction == 'L') dir = { -1, 0 };
    else dir = { 0, -1 };

    while (ins.mp4es > 0) {
        ins.mp4es = ins.mp4es - 1;
        knots[0] += dir;
        for (size_t i{ 1 }; i < knots.size(); ++i) {
            if (knots[i - 1].distance(knots[i]) > std::numbers::sqrt2_v<double>) knots[i] += knots[i].calculate_move_vector(knots[i - 1]);
        }
        v.insert(knots.back());
    }
}


int main()
{
    std::set<Point> visited_part_one;
    std::set<Point> visited_part_two;

    std::vector<Point> partOne{ { 0, 0 } , { 0, 0 } };
    std::vector<Point> partTwo(10);

    std::ifstream file("input.txt");

    std::string line;
    char cmd;
    while (file >> cmd) {
        Instruction ins;
        ins.direction = cmd;
        file >> ins.mp4es;
        move(partOne, ins, visited_part_one);
        move(partTwo, ins, visited_part_two);
    }
    std::cout << "Part One:" << visited_part_one.size() << '\n';
    std::cout << "Part Two:" << visited_part_two.size() << '\n';

    return -1;
}
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In my part one, i just set the tail = previous position of head, if head and tail were >sqrt(2) away, took me way to long, to notice it

Seems to be true even for part2 (have not tested), if so then we are all r-slurs and you're our half-r-slur king.

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No, that implementation works similar to the snake game, but part two requires it to actually work like a rope.

There is a visualisation on reddit that kinda illustrate how it is supposed to work https://old.reddit.com/r/adventofcode/comments/zgq3nr/2022_day_9_rope_pull/ and why just setting the position of the following parts to the old poisition of the current part doesnt work.

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Ah, I see, thank you, the whole rope behavior is different. Interesting.

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That's nice sweaty. Why don't you have a seat in the time out corner with Pizzashill until you calm down, then you can have your Capri Sun.

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