Day8

day8/trees.c

@@ -0,0 +1,130 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFFER_SIZE 128
+#define cti(c) (c - '0')
+
+// For simplicity we know the dimensions
+#define MAP_WIDTH  99
+#define MAP_HEIGHT 99
+
+enum DIRECTION {
+    TOP,
+    RIGHT,
+    BOTTOM,
+    LEFT
+};
+
+int map[MAP_WIDTH][MAP_HEIGHT];
+int visible[MAP_WIDTH][MAP_HEIGHT];
+
+int is_visible_from(int, int, enum DIRECTION, int);
+int is_visible(int, int);
+int scenic_score(int, int);
+
+int scenic[4] = {0,0,0,0};
+
+int main() {
+    char c;
+    int col = 0, row = 0;
+
+    while ((c = getchar()) != EOF) {
+        if (c == '\n') {
+            col = 0;
+            row++;
+            continue;
+        }
+        map[col][row] = cti(c);
+        col++;
+    }
+
+    // Nothing is visible first
+    for (int i = 0; i < MAP_WIDTH; i++)
+        for (int j = 0; j < MAP_HEIGHT; j++)
+            visible[i][j] = 0;
+
+    int sum = 0;
+    // Let's iterate all trees and find if they are visible
+    // It would be cleaner to just run a scan from the edges
+    // and mark trees that are visible (higher than the current max)
+    //
+    // But where's the recursion in that?
+    for (int i = 0; i < MAP_HEIGHT; i++)
+        for (int j = 0; j < MAP_WIDTH; j++) {
+            visible[j][i] = is_visible(j, i);
+            sum += visible[j][i];
+        }
+
+    printf("%i\n", sum);
+
+    int bestScenic = 0, tmp;
+    for (int i = 0; i < MAP_HEIGHT; i++)
+        for (int j = 0; j < MAP_WIDTH; j++) {
+            tmp = scenic_score(j, i);
+            if (bestScenic < tmp) {
+                bestScenic = tmp;
+            }
+        }
+
+    printf("%i\n", bestScenic);
+}
+
+int is_visible_from(int col, int row, enum DIRECTION direction, int size) {
+    // Ugly solution but it is easier to do this to solve task 2
+    if (row != 0 && col != 0 && row != MAP_HEIGHT - 1 && col != MAP_WIDTH - 1)
+        scenic[direction]++;
+    switch (direction) {
+        case TOP:
+            if (row == 0 || (map[col][row-1] < size && is_visible_from(col, row - 1, TOP, size))) {
+                return 1;
+            }
+            break;
+        case RIGHT:
+            if (col == MAP_WIDTH - 1 || (map[col+1][row] < size && is_visible_from(col + 1, row, RIGHT, size))) {
+                return 1;
+            }
+            break;
+        case BOTTOM:
+            if (row == MAP_HEIGHT - 1 || (map[col][row+1] < size && is_visible_from(col, row + 1, BOTTOM, size))) {
+                return 1;
+            }
+            break;
+        case LEFT:
+            if (col == 0 || (map[col-1][row] < size && is_visible_from(col - 1, row, LEFT, size))) {
+                return 1;
+            }
+            break;
+    }
+
+    return 0;
+}
+
+int is_visible(int col, int row) {
+    // If they are on the visibility map
+    if (visible[col][row])
+        return 1;
+
+    if (is_visible_from(col, row, TOP, map[col][row]) || is_visible_from(col, row, RIGHT, map[col][row]) || is_visible_from(col, row, BOTTOM, map[col][row]) || is_visible_from(col, row, LEFT, map[col][row]))
+        return 1;
+
+    return 0;
+}
+
+int scenic_score(int col, int row) {
+    for (int i = 0; i < 4; i++) {
+        scenic[i] = 0;
+    }
+    is_visible_from(col, row, TOP, map[col][row]);
+    is_visible_from(col, row, RIGHT, map[col][row]);
+    is_visible_from(col, row, BOTTOM, map[col][row]);
+    is_visible_from(col, row, LEFT, map[col][row]);
+
+    int result = 1;
+
+    for (int i = 0; i < 4; i++) {
+        result *= scenic[i];
+    }
+
+    return result;
+}