1 files changed, 140 insertions, 0 deletions
diff --git a/Advent-of-Code-2020/AOC-4/main.c b/Advent-of-Code-2020/AOC-4/main.c
new file mode 100644
index 0000000..895dd00
--- /dev/null
+++ b/Advent-of-Code-2020/AOC-4/main.c
@@ -0,0 +1,140 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#if 0
+#define PART_1
+#else
+#define PART_2
+#endif
+
+#if 0
+#define FILE_PATH "example-valid.txt"
+#else
+#define FILE_PATH "input.txt"
+#endif
+
+char fields[8][4] = {"byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid", "cid"};
+
+size_t valid = 0;
+
+void parse()
+{
+    FILE *fp = fopen(FILE_PATH, "r");
+    if(!fp) {
+        fprintf(stderr, "ERROR: Could not open file: %s", FILE_PATH);
+        exit(EXIT_FAILURE);
+    }
+
+    char line[2048] = {0};
+    int field_valid[8] = {0};
+    while(fgets(line, sizeof(line), fp) != NULL)
+    {
+        if(line[0] == '\n' || strncmp(line, "EOF", 3) == 0)
+        {
+            int result = 1;
+            for(int i = 0; i < 7; i++)
+                result *= field_valid[i];
+
+            valid += result;
+            memset(field_valid, 0 , sizeof(field_valid));
+            continue;
+        }
+
+        char *tok = strtok(line, " ");
+        while(tok != NULL)
+        {
+            for(int i = 0; i < 8; i++)
+            {
+                if(strncmp(tok, fields[i], 3) == 0)
+                {
+                    #ifdef PART_1
+                    field_valid[i] = 1;
+                    #endif
+
+                    #ifdef PART_2
+
+                    char *saveptr;
+                    (void)strtok_r(tok, ":", &saveptr);
+                    char *val = strtok_r(NULL, ":", &saveptr);
+                    assert(val != NULL);
+                    assert(strtok_r(NULL, ":", &saveptr) == NULL);
+
+                    if(val[strlen(val)-1] == '\n') val[strlen(val)-1] = '\0';
+
+                    int ival;
+                    switch(i)
+                    {
+                    case 0: ival = atoi(val);
+                        if(ival >= 1920 && ival <= 2002) field_valid[i] = 1;
+                        break;
+                    case 1: ival = atoi(val);
+                        if(ival >= 2010 && ival <= 2020) field_valid[i] = 1;
+                        break;
+                    case 2: ival = atoi(val);
+                        if(ival >= 2020 && ival <= 2030) field_valid[i] = 1;
+                        break;
+                    case 3:
+                        if(strlen(val) == 5)
+                        {
+                            if(!(val[3] == 'c' && val[4] == 'm')) break;
+                            char _val[4] = {0}; _val[0] = val[0];
+                            _val[1] = val[1]; _val[2] = val[2];
+                            ival = atoi(_val);
+                            if(ival >= 150 && ival <= 193) field_valid[i] = 1;
+                        }
+                        if(strlen(val) == 4)
+                        {
+                            if(!(val[2] == 'i' && val[3] == 'n')) break;
+                            char _val[3] = {0}; _val[0] = val[0]; _val[1] = val[1];
+                            ival = atoi(_val);
+
+                            if(ival >= 59 && ival <= 76) field_valid[i] = 1;
+                        }
+
+                        break;
+                    case 4:
+                        int num = 0;
+                        char valid_vals[16] = "0123456789abcdef";
+                        for(int k = 1; k <= strlen(val); k++)
+                            for(int j = 0; j < 16; j++)
+                                if(val[k] == valid_vals[j]) num++;
+
+                        if(val[0] == '#' && num == 6) field_valid[i] = 1;
+                        break;
+                    case 5:
+                        int valid_ecl = 0;
+                        char valid_cols[7][4] = {"amb", "blu", "brn", "gry", "grn", "hzl", "oth"};
+                        for(int k = 0; k < 7; k++)
+                            if(strncmp(val, valid_cols[k], 3) == 0) valid_ecl++;
+
+                        if(valid_ecl == 1) field_valid[i] = 1;
+                        break;
+                    case 6:
+                        int valid_pid = 0;
+                        if(strlen(val) != 9) break;
+                        char valid_nums[10] = "0123456789";
+                        for(int k = 0; k < strlen(val); k++)
+                            for(int j = 0; j < 10; j++)
+                                if(val[k] == valid_nums[j]) valid_pid++;
+
+                        if(valid_pid == 9) field_valid[i] = 1;
+                        break;
+                    }
+                    #endif
+                }
+            }
+            tok = strtok(NULL, " ");
+        }
+    }
+
+    fclose(fp);
+}
+
+int main(void)
+{
+    parse();
+    printf("%ld passports are valid\n", valid);
+    return 0;
+}