From bac106dcf99e1af0253b1d06070e519afea7fc3d Mon Sep 17 00:00:00 2001
From: Peter <peterr.00000@gmail.com>
Date: Thu, 9 Dec 2021 17:01:43 +0800
Subject: [PATCH] Day 9 solutions

---
 9/9-1and2.c | 160 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 160 insertions(+)
 create mode 100644 9/9-1and2.c

diff --git a/9/9-1and2.c b/9/9-1and2.c
new file mode 100644
index 0000000..0fa602e
--- /dev/null
+++ b/9/9-1and2.c
@@ -0,0 +1,160 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include "../check_alloc.h"
+
+// BASIN_STATS DATATYPE
+
+#define TOP_AREAS 3
+
+typedef struct
+{
+    unsigned int risk;
+    unsigned int top_areas;
+} BASIN_STATS;
+
+// GRID DATASTRUCTURE
+typedef struct
+{
+    unsigned int height;
+    bool scanned;
+} CELL;
+typedef struct
+{
+    CELL **grid;
+    unsigned int height; // GRID DIMENSIONS
+    unsigned int width;
+} GRID;
+
+GRID *new_grid(unsigned int height, unsigned int width)
+{
+    GRID *grid = calloc(1, sizeof(GRID));
+    grid->grid = calloc(height, sizeof(CELL));
+    grid->height = height;
+    grid->width = width;
+    return grid;
+}
+
+void print_grid(GRID *grid)
+{
+    for (size_t i = 0; i < grid->height; i++)
+    {
+        for (size_t j = 0; j < grid->width; j++)
+        {
+            printf("%d(%d)", grid->grid[i][j].height, grid->grid[i][j].scanned);
+        }
+        putchar('\n');
+    }
+    putchar('\n');
+}
+
+unsigned int get_value(GRID *grid, size_t y, size_t x)
+{
+    return (x < 0 || y < 0 || x >= grid->width || y >= grid->height || grid->grid[y][x].scanned)
+               ? 10
+               : grid->grid[y][x].height;
+}
+
+//
+
+unsigned int get_basin_area(GRID *grid, size_t i, size_t j)
+{
+    unsigned int height = get_value(grid, i, j);
+    unsigned int area = 1;
+    grid->grid[i][j].scanned = true;
+#define CHECK_ADJACENT(x, y, grid, area)            \
+    if (get_value((grid), (x), (y)) < 9)            \
+    {                                               \
+        (area) += get_basin_area((grid), (x), (y)); \
+    }
+
+    CHECK_ADJACENT(i + 1, j, grid, area);
+    CHECK_ADJACENT(i - 1, j, grid, area);
+    CHECK_ADJACENT(i, j + 1, grid, area);
+    CHECK_ADJACENT(i, j - 1, grid, area);
+#undef CHECK_ADJACENT
+    return area;
+}
+
+int sort_list(const void *x, const void *y)
+{
+    return *(int *)x - *(int *)y;
+}
+
+// PART 1
+BASIN_STATS *get_risk(GRID *grid)
+{
+    BASIN_STATS *basin = calloc(1, sizeof(BASIN_STATS));
+    unsigned int areas[TOP_AREAS + 1] = {0}; // TRACK 3 LARGEST AREAS
+    unsigned int risk = 0;
+    for (size_t i = 0; i < grid->height; i++)
+    {
+        for (size_t j = 0; j < grid->width; j++)
+        {
+            unsigned int height = get_value(grid, i, j);
+            // MINIMUM
+            if (get_value(grid, i + 1, j) > height && get_value(grid, i - 1, j) > height && get_value(grid, i, j + 1) > height && get_value(grid, i, j - 1) > height)
+            {
+                basin->risk += height + 1;
+                areas[0] = get_basin_area(grid, i, j);
+                qsort(areas, TOP_AREAS + 1, sizeof(areas[0]), sort_list);
+            }
+        }
+    }
+    basin->top_areas = 1;
+    for (size_t i = 1; i < TOP_AREAS + 1; i++)
+    {
+        basin->top_areas *= areas[i];
+    }
+    return basin;
+}
+
+//
+
+unsigned int get_lines(char *file)
+{
+    FILE *p_file = fopen(file, "r");
+    unsigned int lines = 0;
+    char c;
+    while ((c = getc(p_file)) != EOF)
+        if (c == '\n')
+            lines++;
+    return lines;
+}
+
+CELL *str_to_line(char *str, size_t len)
+{
+    CELL *line = calloc(len, sizeof(CELL));
+    for (size_t i = 0; i < len; i++)
+    {
+        line[i].height = (str[i] - '0');
+        line[i].scanned = false;
+    }
+    return line;
+}
+
+GRID *read_file(char *file)
+{
+    FILE *p_file = fopen(file, "r");
+    unsigned int n_lines = get_lines(file);
+    char buf[BUFSIZ];
+    fgets(buf, sizeof buf, p_file);
+    unsigned int width = strlen(buf) - 1;
+    GRID *p_grid = new_grid(n_lines, width);
+    size_t i = 0;
+    do
+    {
+        p_grid->grid[i] = str_to_line(buf, width);
+        i++;
+    } while (fgets(buf, sizeof buf, p_file) != NULL);
+    return p_grid;
+}
+
+int main(int argc, char const *argv[])
+{
+    GRID *p_grid = read_file("input");
+    BASIN_STATS *p_basin = get_risk(p_grid);
+    printf("RISK %d AREA %d\n", p_basin->risk, p_basin->top_areas);
+    return 0;
+}