Add C day 1

c/01/Makefile

@@ -0,0 +1,7 @@
+both: p1 p2
+
+p1:
+	gcc -o main1 part_1.c -lcs50
+
+p2:
+	gcc -o main2 part_2.c -lcs50

c/01/part_1.c

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+#include <stdio.h>
+#include <cs50.h>
+#include <string.h>
+
+// The amount of input lines
+const int lines = 1000;
+
+int extract_number(char *text);
+
+int main(void) {
+    int sum = 0;
+
+    for (int i = 0; i < lines; i++) {
+        sum += extract_number(get_string(""));
+    }
+
+    printf("%i\n", sum);
+    return 0;
+}
+
+/* Get the right number from both sides of the string
+*/
+int extract_number(char *text) {
+    int length = strlen(text);
+    int first;
+
+    for (int i = 0; i < length; i++) {
+        char c = text[i];
+
+        if (c >= '0' && c <= '9') {
+            first = c - '0';
+            break;
+        }
+    }
+
+    for (int i = 1; i <= length; i++) {
+        char c = text[length - i];
+
+        if (c >= '0' && c <= '9') {
+            return (first * 10) + (c - '0');
+        }
+    }
+}

c/01/part_2.c

@@ -0,0 +1,108 @@
+#include <cs50.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// The amount of input lines
+const int lines = 1000;
+
+// The amount of numbers that can be found
+const int number_size = 10;
+
+const char numbers[10][6] =
+    { "zero"
+    , "one"
+    , "two"
+    , "three"
+    , "four"
+    , "five"
+    , "six"
+    , "seven"
+    , "eight"
+    , "nine"
+    };
+
+int  extract_number(int *numbers, int size);
+int *find_numbers(char *text);
+int  numbers_size(int *numbers);
+int  starts_with_number(char *text);
+
+int main(void) {
+    int sum = 0;
+
+    for (int i = 0; i < lines; i++) {
+        // Instead of directly looping through the array,
+        // we extract a list of integers first
+        int *ns = find_numbers(get_string(""));
+
+        // Then use that list to increase the sum
+        sum += extract_number(ns, numbers_size(ns));
+
+        // Free all allocated information
+        free(ns);
+    }
+
+    printf("%i\n", sum);
+    return 0;
+}
+
+/* Given a list of integers, combines the first and the last digit to create a
+single number between 0 and 100.
+*/
+int extract_number(int *numbers, int size) {
+    return (numbers[0] * 10) + numbers[size - 1];
+}
+
+// Convert a string to an array of integers
+int *find_numbers(char *text) {
+    int length = strlen(text);
+
+    int *items = malloc(sizeof(int) * length);
+    int cursor = 0;
+
+    for (int i = 0; i < length; i++) {
+        char c = text[i];
+
+        if (c >= '0' && c <= '9') {
+            items[cursor] = c - '0';
+            cursor++;
+        }
+        else {
+            int n = starts_with_number(text + i);
+
+            if (n >= 0) {
+                items[cursor] = n;
+                cursor++;
+            }
+        }
+    }
+
+    items[cursor] = -1;
+
+    return items;
+}
+
+int numbers_size(int *numbers) {
+    int i = 0;
+
+    while (numbers[i] >= 0) {
+        i++;
+    }
+
+    return i;
+}
+
+/* Determine whether a (sub)string starts with a given number.
+*/
+int starts_with_number(char *text) {
+    for (int i = 0; i < number_size; i ++) {
+        if (strstr(text, numbers[i]) == text) {
+            return i;
+        }
+    }
+
+    // If not, return -1
+    return -1;
+}
+
+

shell.nix

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+{ pkgs ? import <nixpkgs> {}
+}:
+pkgs.mkShell {
+    name="dev-environment";
+    buildInputs = [
+        pkgs.libgcc
+        pkgs.libcs50
+        pkgs.valgrind
+    ];
+    shellHook = ''
+        echo "Start developing! :D"
+    '';
+}