Day1 C

day1/c/day1.c

@@ -0,0 +1,118 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define LINE_MAX_LENGTH 256
+#define NUM_0_CHARCODE 48
+#define NUM_9_CHARCODE NUM_0_CHARCODE + 9
+#define PART_2 1
+#define FORWARD 1
+#define BACKWARD -1
+
+char* english_digit_strings[] = {
+    "zero",
+    "one",
+    "two",
+    "three",
+    "four",
+    "five",
+    "six",
+    "seven",
+    "eight",
+    "nine",
+};
+
+#define NUM_OF_DIGITS ((sizeof(english_digit_strings)) / (sizeof(english_digit_strings[0])))
+
+char *english_digit_strings_reversed[NUM_OF_DIGITS];
+
+int get_num(char *p, int dir) {
+    // Check whether it is a number
+    if (*p >= NUM_0_CHARCODE && *p <= NUM_9_CHARCODE) {
+        return *p - NUM_0_CHARCODE;
+    }
+
+    // Check spelled out numbers
+    if (PART_2) {
+        // Check each digit
+        for (int i = 0; i < NUM_OF_DIGITS; i++) {
+            char *reference = dir == FORWARD ? english_digit_strings[i] : english_digit_strings_reversed[i];
+            char *tmp = p;
+            int match = 1;
+            while (*reference != '\0') {
+                if (*tmp != *reference) {
+                    match = 0;
+                    break;
+                }
+                reference++;
+                tmp += dir;
+            }
+
+            if (match) {
+                return i;
+            }
+        }
+    }
+
+    return -1;
+}
+
+char* reverse_string(char* str) {
+    char *p = str;
+    while (*p != '\0') p++;
+
+    int len = p - str;
+
+    char *newstr = (char *)malloc(len + 1);
+    memset(newstr, 0, len + 1);
+    p--;
+
+
+    char* newp = newstr;
+    while (p != str) {
+        *newp = *p;
+        newp++;
+        p--;
+    }
+    *newp = *p;
+
+    return newstr;
+}
+
+void create_reversed_digit_strings() {
+    for (int i = 0; i < NUM_OF_DIGITS; i++) {
+        english_digit_strings_reversed[i] = reverse_string(english_digit_strings[i]);
+    }
+}
+
+int main() {
+    char *p, *buf, c;
+    int sum = 0, n = -1;
+    create_reversed_digit_strings();
+
+    buf = (char *)malloc(LINE_MAX_LENGTH);
+    memset(buf, 0, LINE_MAX_LENGTH);
+    p = buf;
+
+    while ((c = getchar()) != EOF) {
+        *p++ = c;
+        if (c == '\n') {
+            // Find last number (p points to the end of line)
+            while ((n = get_num(p, BACKWARD)) == -1) p--;
+            sum += n;
+            // Find first number
+            p = buf;
+            while ((n = get_num(p, FORWARD)) == -1) p++;
+            sum += n * 10;
+
+            memset(buf, 0, LINE_MAX_LENGTH);
+            p = buf;
+        }
+    }
+
+    free(buf);
+    for (int i = 0; i < NUM_OF_DIGITS; i++) {
+        free(english_digit_strings_reversed[i]);
+    }
+    printf("%i\n", sum);
+}

day1/sample.txt

@@ -0,0 +1,4 @@
+1abc2
+pqr3stu8vwx
+a1b2c3d4e5f
+treb7uchet

day1/sample2.txt

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+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen