Day 8

src/Days/D08.c

@@ -0,0 +1,195 @@
+#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);
+
+
+// }