Advent2017_12b

#include <sstream>
#include <iostream>
#include <fstream>

const unsigned int MAX_LAYERS = 100;

// https://pastebin.com/bNAaTL1e

void updateLayer(unsigned int * layer) {
    unsigned int range = layer[0];
    unsigned int position = layer[1];
    unsigned int direction = layer[2];
    if(direction == 0) {
        // down v
        if(position == range - 1) {
            layer[1] = range - 2;
            layer[2] = 1; // change direction to up
        }else {
            layer[1]++;
        }
    }else {
        // up ^
        if(position == 0) {
            layer[1] = 1; // second position
            layer[2] = 0; // go down
        }else {
            layer[1]--;
        }
    }
}

int main(int argc, char ** argv) {
    std::ifstream inputFile("input.txt");

    unsigned int ** layers = new unsigned int * [MAX_LAYERS];
    unsigned int ** delayState = new unsigned int * [MAX_LAYERS];
    for(unsigned int i = 0; i < MAX_LAYERS; i++) {
        layers[i] = new unsigned int[3];
        layers[i][0] = 0; // range
        layers[i][1] = 0; // current scanner position
        layers[i][2] = 0; // current scanner direction (0 down, 1 up)

        delayState[i] = new unsigned int[3];
        delayState[i][0] = 0; // range
        delayState[i][1] = 0; // current scanner position
        delayState[i][2] = 0; // current scanner direction (0 down, 1 up)
    }

    if(!inputFile.is_open()) {
        std::cout << "Could not read file." << std::endl;
        return 1;
    }

    std::string line;
    while(std::getline(inputFile, line)) {
        std::stringstream ss(line);

        unsigned int source = 0;
        unsigned int range = 0;
        ss >> source;

        ss.ignore(1, ':');
        ss.ignore(1);

        ss >> range;
        layers[source][0] = range;
        delayState[source][0] = range;
    }

    unsigned int delay = 0;

    while(true) {
        // Reset layers to next delay state:
        for(unsigned int i = 0; i < MAX_LAYERS; i++) {
            layers[i][1] = delayState[i][1]; // current scanner position
            layers[i][2] = delayState[i][2]; // direction
        }

        // Look for crashes:
        bool crash = false;
        for(unsigned int depth = 0; depth < MAX_LAYERS; depth++) {
            unsigned int * currentLayer = layers[depth];

            if(currentLayer[0] > 0 && currentLayer[1] == 0) {
                crash = true;
                break;
            }

            // Update all layers from current depth onward:
            for(unsigned int i = depth; i < MAX_LAYERS; i++) {
                updateLayer(layers[i]);
            }
        }

        if(!crash) {
            break;
        }

        // Next delay state simulation
        for(unsigned int i = 0; i < MAX_LAYERS; i++) {
            updateLayer(delayState[i]);
        }

        delay++;
    }

    std::cout << "Delay: " << delay << std::endl;

    return 0;
}