lab13

lab13/lab13.c

+#include <time.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <string.h>
+#include <ctype.h>
+
+
+
+
+void encrypt(char *mes,int k);
+;
+int main(void){
+    char mes;
+    int a;
+    printf("enter message\n");
+    scanf("%s",&mes);
+    puts(&mes);
+    int k;
+    printf("enter key");
+    scanf("%d",&k);
+    printf("%d",k);
+
+    printf("do you want to 1-encrypt or 2-Decrypt? 1,2"); //there is no safety f the user enters another value than expected because i believe this is beside the point of the exercise
+    scanf("%d",&a);
+
+
+    if (a==1){
+        encrypt(&mes,k);
+    }
+    else if (a==2){
+        encrypt(&mes,-k);
+    }
+    else {printf("none");}
+    return 0;
+}
+
+void encrypt(char *mes,int k){
+    int len = strlen(mes);
+    int i;
+    char *new = NULL;
+    new = calloc(len + 1, sizeof(char));
+
+    for (i = 0; i < len; i++) {
+        char c = mes[i];
+        int c_int = (int) c;
+
+        if (!isalpha(c_int)) {
+            new[i] = mes[i];
+            continue;
+        }
+
+        if (isupper(c_int)) {
+            new[i] = (((c_int - 'A') + k) % 26) + 'A';
+            if (new[i] < 'A') {
+                new[i] = 'Z' + 1 - ('A' - new[i]);
+            }
+        } else {
+            new[i] = (((c_int - 'a') + k) % 26) + 'a';
+            if (new[i] < 'a') {
+                new[i] = 'z' + 1 - ('a' - new[i]);
+            }
+        }
+    }
+
+
+    printf("result message: %s", new);
+
+}
+