aoc-2022/src/Days/D08.c

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

struct result_cell
{
    int32_t fst;
    int32_t snd;
};

struct stack_cell
{
    char c;
    int32_t p;
};

struct stack
{
    struct stack_cell stk[10];
    int32_t height;
};

struct stack init_stack()
{
    struct stack result;
    result.height = 0;
    return result;
}

void stack_push(struct stack* stk, struct stack_cell v)
{
    stk->stk[stk->height] = v;
    stk->height++;
}

void stack_pop(struct stack *stk)
{
    stk->height--;
}

struct stack_cell stack_top(struct stack *stk)
{
    return stk->stk[stk->height - 1];
}

bool stack_empty(struct stack *stk)
{
    return stk->height == 0;
}

void analyze_row(
    char grid[], 
    bool result_visible[],
    int32_t result_fwd[],
    int32_t result_bwd[],
    int32_t row,
    int32_t w,
    int32_t xs,
    int32_t ys)
{
    struct stack stk = init_stack();
    struct stack_cell top;
    int32_t j = 0;
    char cur;
    size_t pos;


    stack_push(&stk, (struct stack_cell) { '9' + 1, 0}); //sentinel

    for (; j < w; j++) {
        pos = row*xs+j*ys;
        cur = grid[pos];

        while (stk.height > 0
            && (top = stack_top(&stk)).c < cur) {
            result_fwd[row*xs+(top.p)*ys] = j - top.p;
            stack_pop(&stk);
        }

        if (stk.height == 1) {
            result_visible[row*xs+j*ys] = true;
        }

        result_bwd[pos] = j - top.p;

        if (top.c == cur) {
            result_fwd[row*xs+(top.p)*ys] = j - top.p;
            stack_pop(&stk);
        }
        stack_push(&stk, (struct stack_cell) { cur, j});
    }

    while (stk.height > 1) {
        top = stack_top(&stk);
        result_fwd[row*xs+(top.p)*ys] = w - top.p - 1;
        result_visible[row*xs+(top.p)*ys] = true;
        stack_pop(&stk);
    }
}

void analyze(
    char grid[],
    bool result_visible[],
    int32_t result_fwd[],
    int32_t result_bwd[],
    int32_t h,
    int32_t w,
    int32_t xs,
    int32_t ys)
{
    for (int32_t i = 0; i < h; i++) {
        analyze_row(grid, result_visible, result_fwd, result_bwd, i, w, xs, ys);
    }
}

// void analyze_horizontal(char grid[], int32_t result_fwd[], int32_t result_bwd[], int32_t height, int32_t width)
// {
//     analyze(grid, result_fwd, result_bwd, height, width, width, 1);
// }


// void analyze_vertical(char grid[], int32_t result_fwd[], int32_t result_bwd[], int32_t height, int32_t width)
// {
//     analyze(grid, result_fwd, result_bwd, height, width, 1, height);
// }

// void print_grid(char grid[], int h, int w) {
//     for (int i = 0; i < h; i++) {
//         for (int j = 0; j < w; j++) {
//             putchar(grid[i*w + j]);
//             putchar(' ');
//         }
//         putchar('\n');
//     }
// }
// void print_result(int grid[], int h, int w) {
//     for (int i = 0; i < h; i++) {
//         for (int j = 0; j < w; j++) {
//             printf("%d ", grid[i*w+j]);
//         }
//         putchar('\n');
//     }
// }

// int main()
// {
//     FILE *fp = fopen("./data/08.in", "r");

//     // Determine file size
//     fseek(fp, 0L, SEEK_END);
//     int fpsize = ftell(fp);
//     fseek(fp, 0L, SEEK_SET);
//     rewind(fp);

//     char *buf = malloc(fpsize);
//     char *grid = malloc(fpsize);
    
//     fread(buf, 1, fpsize, fp);
//     char *grid_ptr = grid;
//     for (int i = 0; i < fpsize; i++) {
//         *grid_ptr = buf[i];
//         if (buf[i] != '\n') {
//             grid_ptr++;
//         }
//     }

//     int H = 5;
//     int W = 5;

//     print_grid(grid, H, W);

//     int* result_fwd = malloc(fpsize * sizeof(int));
//     int* result_bwd = malloc(fpsize * sizeof(int));

//     analyze_vertical(grid, result_fwd, result_bwd, H, W);

//     printf("\n D \n");
//     print_result(result_fwd, H, W);

//     printf("\n U \n");
//     print_result(result_bwd, H, W);


//     analyze_horizontal(grid, result_fwd, result_bwd, H, W);


//     printf("\n R \n");
//     print_result(result_fwd, H, W);

//     printf("\n L \n");
//     print_result(result_bwd, H, W);


// }