AoC22/d08.cc

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>

using namespace std;

typedef vector<vector<unsigned char>> Input;

Input parse()
{
    Input data;
    for (string line; getline(cin, line);) {
        auto i = vector<unsigned char>(line.begin(), line.end());
        for_each(i.begin(), i.end(), [](unsigned char &x){ x -= '0'; });
        data.push_back(i);
    }
    return data;
}

unsigned p1(const Input &trees)
{
    int height = trees.size();
    int width = trees.front().size();

    // C++ is nice except when it isn't
    bool (*vis)[width] = (bool (*)[width])new bool[width * height];
    memset(vis, 0, sizeof(bool) * width * height);

    // The corners are visible
    vis[0][0] = true;
    vis[height - 1][0] = true;
    vis[0][width - 1] = true;
    vis[height - 1][width - 1] = true;

    // Determine visibility from all four directions
    for (int y = 1; y < height - 1; y++) {
        for (int last = -1, x = 0; x < width; x++) {
            if (trees[y][x] <= last) continue;
            last = trees[y][x];
            vis[y][x] = true;
        }
        for (int last = -1, x = width - 1; x >= 0; x--) {
            if (trees[y][x] <= last) continue;
            last = trees[y][x];
            vis[y][x] = true;
        }
    }
    for (int x = 1; x < width - 1; x++) {
        for (int last = -1, y = 0; y < height; y++) {
            if (trees[y][x] <= last) continue;
            last = trees[y][x];
            vis[y][x] = true;
        }
        for (int last = -1, y = height - 1; y >= 0; y--) {
            if (trees[y][x] <= last) continue;
            last = trees[y][x];
            vis[y][x] = true;
        }
    }

    // Count 'em up
    unsigned count = 0;
    for (int y = 0; y < height; y++) {
        for (int x = 0; x < width; x++) if (vis[y][x]) count++;
    }

    // Debug
    //for (int y = 0; y < height; y++) {
        //for (int x = 0; x < width; x++) clog << (char)(vis[y][x] ? 'x' : ' ');
        //clog << endl;
    //}

    delete vis;
    return count;
}

unsigned p2(const Input &trees)
{
    int height = trees.size();
    int width = trees.front().size();

    unsigned score = 0;
    for (int y = 1; y < height - 1; y++) {
        for (int x = 1; x < width - 1; x++) {
            unsigned tree = trees[y][x];

            // Check all four directions
            unsigned cur = 1;
            unsigned c;
            c = 1;
            for (int ny = y + 1; ny < height - 1 && trees[ny][x] < tree; ny++) c++;
            cur *= c;
            c = 1;
            for (int ny = y - 1; ny > 0 && trees[ny][x] < tree; ny--) c++;
            cur *= c;
            c = 1;
            for (int nx = x + 1; nx < height - 1 && trees[y][nx] < tree; nx++) c++;
            cur *= c;
            c = 1;
            for (int nx = x - 1; nx > 0 && trees[y][nx] < tree; nx--) c++;
            cur *= c;

            if (cur > score) score = cur;
        }
    }

    return score;
}

int main()
{
    auto input = parse();
    cout << p1(input) << endl;
    cout << p2(input) << endl;
}