commit 39192ec9f64bbb27bc451beab2ded9e1f86e8629
Author: bot50 <bot@cs50.harvard.edu>
Date:   Sat Feb 24 20:16:06 2024 +0000

    kukemuna-cs50/problems/2024/x/caesar@20240224T201606.557524781Z

diff --git a/caesar.c b/caesar.c
new file mode 100644
index 0000000..fe79c84
--- /dev/null
+++ b/caesar.c
@@ -0,0 +1,86 @@
+#include <cs50.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+int key_to_int_reduced(string s_key);
+void rotate(string plaintext, int i_key);
+
+int main(int argc, string argv[])
+{
+    // Print usage and exit if argc is not 2 or key is not integer
+    if (argc != 2 || key_to_int_reduced(argv[1]) < 0)
+    {
+        printf("Usage: ./caesar key\n");
+        return 1;
+    }
+    else
+    {
+        string s_key = argv[1];
+        int i_key = key_to_int_reduced(s_key);
+        string plaintext = get_string("plaintext:  ");
+        rotate(plaintext, i_key);
+    }
+    return 0;
+}
+
+// Convert a string of numbers to integer
+int key_to_int_reduced(string s_key)
+{
+    int key = 0;
+
+    // Iterate each string element
+    for (int i = 0; i < strlen(s_key); i++)
+    {
+        if (isdigit(s_key[i]))
+        {
+            key += ((int) s_key[i] - 48);
+            if (i < strlen(s_key) - 1)
+            {
+                key *= 10;
+            }
+        }
+        // Cancel if not digit
+        else
+        {
+            return -1;
+        }
+    }
+
+    // Reduce key size to < 26
+    while (key >= 26)
+    {
+        key %= 26;
+    }
+    return key;
+}
+
+void rotate(string plaintext, int i_key)
+{
+    printf("ciphertext: ");
+
+    // Iterate each plaintext element
+    for (int i = 0; i < strlen(plaintext); i++)
+    {
+        // Apply key for text characters only
+        if (isalpha(plaintext[i]))
+        {
+            // Rollover and rotate characters, upper- and lowercase
+            if ((isupper(plaintext[i]) && plaintext[i] + i_key > 90) || (islower(plaintext[i]) && plaintext[i] + i_key > 122))
+            {
+                printf("%c", plaintext[i] + i_key - 26);
+            }
+            // Rotate characters
+            else
+            {
+                printf("%c", plaintext[i] + i_key);
+            }
+        }
+        // Leave non-alphanumerics as-is
+        else
+        {
+            printf("%c", plaintext[i]);
+        }
+    }
+    printf("\n");
+}