day one in raw C

day-1/Makefile

@@ -0,0 +1,7 @@
+.PHONY: all
+
+all:
+	mkdir -p ./bin
+	gcc ./src/main.c -o ./bin/main
+	./bin/main
+

day-1/src/main.c

@@ -0,0 +1,229 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+const char *read_input() {
+  char *file_name = "./src/input.txt";
+
+  FILE *fileptr;
+
+  fileptr = fopen(file_name, "r");
+
+  if (fileptr) {
+    // read entire file into a buffer on heap
+    char *buffer = 0;
+    long length;
+    fseek(fileptr, 0, SEEK_END);
+    length = ftell(fileptr);
+    fseek(fileptr, 0, SEEK_SET);
+    buffer = malloc(length);
+    if (buffer) {
+      fread(buffer, 1, length, fileptr);
+    }
+    fclose(fileptr);
+
+    return buffer;
+  } else {
+    printf("not able to open file");
+  }
+
+  fclose(fileptr);
+
+  return "";
+}
+
+// given lines of text, combine first and last number of each line and sum all
+// of those combined numbers
+int getSum(const char text[]) {
+  // get one line at a time
+  char *curr_line = strtok(text, "\n");
+
+  int total = 0;
+
+  while (curr_line != NULL) {
+    // printf("curr_line: %s\n", curr_line);
+
+    int first_num = 0;
+    int last_num = 0;
+
+    for (int i = 0; i < strlen(curr_line); i++) {
+      char curr_char = curr_line[i];
+      if (curr_char >= '0' && curr_char <= '9') {
+        first_num = curr_char - '0';
+        break;
+      }
+    }
+    for (int i = strlen(curr_line) - 1; i >= 0; i--) {
+      char curr_char = curr_line[i];
+      if (curr_char >= '0' && curr_char <= '9') {
+        last_num = curr_char - '0';
+        break;
+      }
+    }
+
+    // printf("first: %d\n", first_num);
+    // printf("last: %d\n", last_num);
+
+    // combine 1 and 9 to 19
+    int combined;
+    if (first_num > 0 && last_num > 0) {
+      combined = first_num * 10 + last_num;
+    } else {
+      combined = first_num + last_num;
+    }
+
+    // printf("combined: %d\n", combined);
+    total += combined;
+
+    curr_line = strtok(NULL, "\n");
+  }
+
+  return total;
+}
+
+// helper: return number if the given string contains a number
+int check_if_string_contains(char *substr) {
+  if (strstr(substr, "one") != NULL) {
+    return 1;
+  }
+  if (strstr(substr, "two") != NULL) {
+    return 2;
+  }
+  if (strstr(substr, "three") != NULL) {
+    return 3;
+  }
+  if (strstr(substr, "four") != NULL) {
+    return 4;
+  }
+  if (strstr(substr, "five") != NULL) {
+    return 5;
+  }
+  if (strstr(substr, "six") != NULL) {
+    return 6;
+  }
+  if (strstr(substr, "seven") != NULL) {
+    return 7;
+  }
+  if (strstr(substr, "eight") != NULL) {
+    return 8;
+  }
+  if (strstr(substr, "nine") != NULL) {
+    return 9;
+  }
+
+  return 0;
+}
+
+int get_sum_part_two(char *text) {
+  // get one line at a time
+  char *curr_line = strtok(text, "\n");
+
+  int total = 0;
+
+  while (curr_line != NULL) {
+    // printf("curr_line: %s\n", curr_line);
+
+    int first_num = 0;
+    int last_num = 0;
+
+    for (int i = 0; i < strlen(curr_line); i++) {
+      char curr_char = curr_line[i];
+      if (curr_char >= '0' && curr_char <= '9') {
+        first_num = curr_char - '0';
+        break;
+      }
+      char substr[i + 1];
+      strncpy(substr, curr_line, i + 1);
+      substr[i + 1] = '\0';
+      // printf("substr: %s\n", substr);
+      int num = check_if_string_contains(substr);
+      if (num > 0) {
+        first_num = num;
+        break;
+      }
+    }
+    for (int i = strlen(curr_line) - 1; i >= 0; i--) {
+      char curr_char = curr_line[i];
+      if (curr_char >= '0' && curr_char <= '9') {
+        last_num = curr_char - '0';
+        break;
+      }
+
+      int len = strlen(curr_line) - i;
+      char substr[len];
+      strncpy(substr, curr_line + i, len);
+      substr[len] = '\0';
+      // printf("ending substr: %s\n", substr);
+      int num = check_if_string_contains(substr);
+      if (num > 0) {
+        // printf("found num: %d\n", num);
+        last_num = num;
+        break;
+      }
+    }
+
+    // printf("first: %d\n", first_num);
+    // printf("last: %d\n", last_num);
+
+    // combine 1 and 9 to 19
+    int combined;
+    if (first_num > 0 && last_num > 0) {
+      combined = first_num * 10 + last_num;
+    } else {
+      combined = first_num + last_num;
+    }
+
+    // printf("combined: %d\n", combined);
+    total += combined;
+
+    curr_line = strtok(NULL, "\n");
+  }
+
+  return total;
+}
+
+// returns 1 if test passes, 0 if test fails
+int test() {
+  char test_input[] = "1abc2\npqr3stu8vwx\na1b2c3d4e5f\ntreb7uchet";
+  int total = getSum(test_input);
+
+  if (total == 142) {
+    return 1;
+  } else {
+    return 0;
+  }
+}
+
+int test_part_two() {
+  char test_input[] = "two1nine\neightwothree\nabcone2threexyz\nxtwone3four\n4n"
+                      "ineeightseven2\nzoneight234\n7pqrstsixteen";
+  int total = get_sum_part_two(test_input);
+  return total == 281;
+}
+
+int main() {
+  printf("Hello, world!\n");
+
+  printf("running test");
+  int test_result = test();
+  printf("test result: %d\n", test_result);
+
+  printf("reading input");
+  const char *input = read_input();
+  // printf("input: %s\n", input);
+
+  int result = getSum(input);
+  printf("result: %d\n", result);
+
+  printf("running test part two");
+  int test_result_part_two = test_part_two();
+  printf("test result part two: %d\n", test_result_part_two);
+
+
+  const char* input_part_two = read_input();
+  int result_part_two = get_sum_part_two(input_part_two);
+  printf("result part two: %d\n", result_part_two);
+
+  return 0;
+}