Move all Advent of Codes into one repo

1 files changed, 135 insertions, 0 deletions

diff --git a/2020/04/part2.c b/2020/04/part2.c
new file mode 100644
index 0000000..5aac219
--- /dev/null
+++ b/2020/04/part2.c
@@ -0,0 +1,135 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define KEYS_LEN 7
+const char* const keys[] = { "byr:", "iyr:", "eyr:", "hgt:", "hcl:", "ecl:", "pid:" };
+
+bool is_valid_field(const char *key, const char *value)
+{
+    if (strncmp(key, "byr", 3) == 0) {
+        int v = atoi(value);
+        return v >= 1920 && v <= 2002;
+    }
+
+    if (strncmp(key, "iyr", 3) == 0) {
+        int v = atoi(value);
+        return v >= 2010 && v <= 2020;
+    }
+
+    if (strncmp(key, "eyr", 3) == 0) {
+        int v = atoi(value);
+        return v >= 2020 && v <= 2030;
+    }
+
+    if (strncmp(key, "hgt", 3) == 0) {
+        int v = atoi(value);
+        if (strncmp(value + 3, "cm", 2) == 0) {
+            return v >= 150 && v <= 193;
+        }
+
+        if (strncmp(value + 2, "in", 2) == 0) {
+            return v >= 59 && v <= 76;
+        }
+
+        return false;
+    }
+
+    if (strncmp(key, "hcl", 3) == 0) {
+        if (value[0] != '#') {
+            return false;
+        }
+
+        for (int i = 1; i < 7; i++) {
+            if (!(value[i] >= 48 && value[i] <= 57) && !(value[i] >= 97 && value[i] <= 102)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    if (strncmp(key, "ecl", 3) == 0) {
+        return strncmp(value, "amb", 3) == 0
+            || strncmp(value, "blu", 3) == 0
+            || strncmp(value, "brn", 3) == 0
+            || strncmp(value, "gry", 3) == 0
+            || strncmp(value, "grn", 3) == 0
+            || strncmp(value, "hzl", 3) == 0
+            || strncmp(value, "oth", 3) == 0;
+    }
+
+    if (strncmp(key, "pid", 3) == 0) {
+        for (int i = 0; i < 9; i++) {
+            if (!(value[i] >= 48 && value[i] <= 57)) {
+                return false;
+            }
+        }
+
+        return !(value[9] >= 48 && value[9] <= 57);
+    }
+
+    return false;
+}
+
+bool is_valid_passport(const char *pass)
+{
+    for (int i = 0; i < KEYS_LEN; i++) {
+        const char *p = strstr(pass, keys[i]);
+        if (!p) {
+            return false;
+        }
+
+        if (!is_valid_field(p, p + 4)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+int count_valid_passports(const char *filename)
+{
+    FILE *file = fopen(filename, "r");
+
+    // Include space for newline and string terminator
+    char buffer[128] = { 0 };
+
+    uint8_t values = 0;
+    int correct = 0;
+    while (fgets(buffer, 128, file)) {
+        if (buffer[0] == '\n') {
+            if (values == 0x7f) {
+                correct++;
+            }
+
+            values = 0;
+        }
+
+        for (int i = 0; i < KEYS_LEN; i++) {
+            const char *p = strstr(buffer, keys[i]);
+            if (!p) {
+                continue;
+            }
+
+            if (is_valid_field(p, p + 4)) {
+                values = values | (0x1 << i);
+            }
+        }
+    }
+
+    if (values == 0x7f) {
+        correct++;
+    }
+
+    fclose(file);
+
+    return correct;
+}
+
+int main(int argc, char *argv[])
+{
+    printf("%i", count_valid_passports(argv[argc - 1]));
+}