From e547d91e825f5f7b305a2f59c4694c9e3007e253 Mon Sep 17 00:00:00 2001
From: Peter <peterr.00000@gmail.com>
Date: Sun, 5 Dec 2021 19:20:09 +0800
Subject: [PATCH] Day 5 solutions

---
 5/5-1and2.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 5/5-1and2.c

diff --git a/5/5-1and2.c b/5/5-1and2.c
new file mode 100644
index 0000000..0717530
--- /dev/null
+++ b/5/5-1and2.c
@@ -0,0 +1,133 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+// PART 2 - DIAGONAL_LINES
+#define PART_2
+
+// SPACE
+
+#define SPACE_SIZE 1000
+
+typedef unsigned int **SPACE;
+
+void print_space(SPACE space)
+{
+    for (size_t i = 0; i < SPACE_SIZE; i++)
+    {
+        for (size_t j = 0; j < SPACE_SIZE; j++)
+        {
+            if (space[j][i] == 0)
+                putchar('.');
+            else
+                printf("%d", space[j][i]);
+        }
+        putchar('\n');
+    }
+    putchar('\n');
+}
+
+unsigned int count_intersections(SPACE space)
+{
+    unsigned int count = 0;
+    for (size_t i = 0; i < SPACE_SIZE; i++)
+    {
+        for (size_t j = 0; j < SPACE_SIZE; j++)
+        {
+            if (space[j][i] > 1)
+                count++;
+        }
+    }
+    return count;
+}
+
+//
+// LINE
+
+typedef struct
+{
+    int x1;
+    int y1;
+    int x2;
+    int y2;
+} LINE;
+
+void swap(unsigned int *v1, unsigned int *v2)
+{
+    unsigned int buf = *v1;
+    *v1 = *v2;
+    *v2 = buf;
+}
+
+// void print_line(LINE *line)
+// {
+//     printf("[%d,%d]->[%d,%d]\n", line->x1, line->y1, line->x2, line->y2);
+// }
+
+#ifndef PART_2
+bool is_straight_line(LINE *line)
+{
+    return line->x1 == line->x2 || line->y1 == line->y2;
+}
+#endif
+
+bool plot_line(LINE *line, SPACE space)
+{
+    int dx = line->x2 - line->x1;
+#ifndef PART_2
+    if (!is_straight_line(line)) //PART 1
+        return false;
+#endif
+    int dy = line->y2 - line->y1;
+    if (dx == 0 || abs(dy / dx) > 1)
+    {
+        int b = line->x1 - dx / dy * line->y1;
+        if (dy < 0)
+            swap(&line->y1, &line->y2);
+        for (int y = line->y1; y <= line->y2; y++)
+        {
+            int x = dx / dy * y + b;
+            space[x][y]++;
+        }
+    }
+    else
+    {
+        int b = line->y1 - dy / dx * line->x1;
+        if (dx < 0)
+            swap(&line->x1, &line->x2);
+        for (int x = line->x1; x <= line->x2; x++)
+        {
+            int y = dy / dx * x + b;
+            space[x][y]++;
+        }
+    }
+}
+
+void read_space_file(FILE *file, SPACE space)
+{
+    char buf[BUFSIZ];
+    LINE *line = calloc(1, sizeof(LINE));
+    while (fscanf(file, "%d,%d -> %d,%d\n", &line->x1, &line->y1, &line->x2, &line->y2) == 4)
+    {
+        plot_line(line, space);
+    }
+}
+
+int main(int argc, char const *argv[])
+{
+    FILE *p_file = fopen("input", "r");
+
+    // MAKE SPACE
+    SPACE space = calloc(SPACE_SIZE, sizeof(unsigned int *));
+    for (size_t i = 0; i < SPACE_SIZE; i++)
+    {
+        space[i] = calloc(SPACE_SIZE, sizeof(unsigned int));
+    }
+    //
+
+    read_space_file(p_file, space);
+    print_space(space);
+    printf("%d\n", count_intersections(space));
+    return 0;
+}