day 3

1 files changed, 92 insertions, 0 deletions

diff --git a/Advent-of-Code-2022/aoc-3/main.c b/Advent-of-Code-2022/aoc-3/main.c
new file mode 100644
index 0000000..d8e5815
--- /dev/null
+++ b/Advent-of-Code-2022/aoc-3/main.c
@@ -0,0 +1,92 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if 0
+  #define PART part1
+#else
+  #define PART part2
+#endif
+
+#if 0
+  #define FILENAME "sample.txt"
+#else
+  #define FILENAME "input.txt"
+#endif
+
+int sum = 0;
+
+int char_to_index(char ch)
+{
+    if(ch >= 'a')
+        return ch - 'a';
+    return ch - 'A' + 26;
+}
+
+void part1(char *line)
+{
+    int times_seen[56] = {0};
+    int leftest[56]    = {0}; // rightest position of that character seen
+    int rightest[56]   = {0}; // leftest position of that character seen
+
+    int len = strlen(line);
+    len = (len % 2) ? len : len - 1; // fgets reads the new line and the last line has no newline
+    for(int i = 0; i < len; i++)
+    {
+        int ch = char_to_index(line[i]);
+        times_seen[ch]++;
+        if(times_seen[ch] == 1)
+            leftest[ch] = i;
+        else
+            rightest[ch] = i;
+
+        if(times_seen[ch] > 1)
+            if(leftest[ch] < len/2 && rightest[ch] >= len/2) {
+                sum += ch + 1;
+                break;
+            }
+    }
+}
+
+int gn = 0;
+int times_seen[56][3] = {0};
+
+void part2(char *line)
+{
+    for(int i = 0; line[i] != '\n' && line[i] != '\0'; i++)
+        times_seen[char_to_index(line[i])][gn]++;
+    gn++;
+
+    if(gn == 3) {
+        for(int j = 0; j < 56; j++)
+            if(times_seen[j][0] && times_seen[j][1] && times_seen[j][2]) {
+                sum += j + 1;
+                break;
+            }
+        gn = 0;
+        memset(times_seen, 0, sizeof(times_seen));
+    }
+
+}
+
+void parse()
+{
+    FILE *fp = fopen(FILENAME, "r");
+    if(!fp) {
+        fprintf(stderr, "ERROR: Could not open file: %s\n", FILENAME);
+        exit(1);
+    }
+
+    char line[256];
+    while(fgets(line, sizeof(line), fp) != NULL)
+        PART(line);
+
+    fclose(fp);
+}
+
+int main(void)
+{
+    parse();
+    printf("%d\n", sum);
+    return 0;
+}