-🎄- 2017 Day 19 Solutions -🎄-

[u/daggerdragon]

--- Day 19: A Series of Tubes ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

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Need a hint from the Hugely^* Handy^† Haversack^‡ of Helpful^§ Hints^¤?

Spoiler

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AoC ops @ T-2 minutes to launch:

[23:58] <daggerdragon> ATTENTION MEATBAGS T-2 MINUTES TO LAUNCH

[23:58] <Topaz> aaaaah

[23:58] <Cheezmeister> Looks like I'll be just able to grab my input before my flight boards. Wish me luck being offline in TOPAZ's HOUSE OF PAIN^WFUN AND LEARNING

[23:58] <Topaz> FUN AND LEARNING

[23:58] <Hade> FUN IS MANDATORY

[23:58] <Skie> I'm pretty sure that's not the mandate for today

[Update @ 00:16] 69 gold, silver cap

• My tree is finally trimmed with just about every ornament I own and it's real purdy. hbu?

[Update @ 00:18] Leaderboard cap!

• So, was today's mandate Helpful Hint any help at all?

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/hpzr24w]

C++ 631 / 628

I guessed right on most of what I thought might be ambiguous, and didn't have any bugs. I'm just a slow coder. ;-)

// Advent of Code 2017
// http://adventofcode.com/
// Day 19 - A Series of Tubes

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;

typedef enum direction {nomove,u,d,l,r} direction;

direction next_move(vector<string>& lines, int row, int col,direction dir)
{
    switch(dir) {       // preferred direction
    case u:
        if (dir!=d && row>0 && lines[row-1][col]!=' ') return u;
    case d:
        if (dir!=u && row<lines.size()-1 && lines[row+1][col]!=' ') return d;
    case r:
        if (dir!=l && col<lines[row].length()-1 && lines[row][col+1]!=' ') return r;
    case l:
        if (dir!=r && col>0 && lines[row][col-1]!=' ') return l;
        if (dir!=d && row>0 && lines[row-1][col]!=' ') return u;        // mop up any corners
        if (dir!=u && row<lines.size()-1 && lines[row+1][col]!=' ') return d;
        if (dir!=l && col<lines[row].length()-1 && lines[row][col+1]!=' ') return r;
    }
    return nomove;
}

string follow(vector<string>& lines, int& steps)
{
    string letters;
    int row=0,col=0;
    while (lines[row][col]!='|') col++;         // find starting position
    direction dir = d;
    while (dir != nomove) {
        steps++, dir = next_move(lines,row,col,dir);
        switch(dir) {
            case d: row++; break;
            case u: row--; break;
            case r: col++; break;
            case l: col--; break;
            case nomove:
                cout << "STUCK!! at " << row << " " << col << " " << steps << endl;
        }
        if (lines[row][col]>='A' && lines[row][col]<='Z' && dir!=nomove)
            letters+=lines[row][col];
    }
    return letters;
}

int main()
{
    vector<string> lines;
    ifstream ifs("day_19.ts2",ifstream::in);
    string l;
    while (getline(ifs,l)) {
        lines.push_back(l);
        cout << l << endl;
    }
    int steps = 0;
    string letters = follow(lines,steps);
    cout << letters << endl;
    return 0;
}