Created
July 13, 2021 17:19
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#include <stdio.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <ctype.h> | |
#include <cs50.h> | |
// plaintext (p) vs ciphertex (c), and a key (k) | |
// “rotate” each (alphabetical) character by k positions | |
// Your program must accept a single command-line argument, a non-negative integer | |
// Your program must preserve case | |
// lowercase: 65(a) - 90(z) | |
// uppercase: 97(a) - 122(z) | |
// isalpha, islower, isupper, isdigit | |
int main(int argc, string argv[]) | |
{ | |
if (argc == 2) | |
{ | |
for (int i = 0; i < strlen(argv[1]); i++) | |
{ | |
if (isdigit(argv[1][i]) == 0) | |
{ | |
printf("Usage: ./caesar k\n"); | |
return 1; | |
} | |
} | |
// atoi convert a string to an int | |
int k = atoi(argv[1]); | |
string p = get_string("plaintext: "); | |
printf("ciphertext: "); | |
for (int i = 0, len = strlen(p); i < len; i++) | |
{ | |
if (islower(p[i])) | |
{ | |
printf("%c", (((p[i] - 'a') + k) % 26) + 'a'); | |
} | |
else if (isupper(p[i])) | |
{ | |
printf("%c", (((p[i] - 'A') + k) % 26) + 'A'); | |
} | |
else | |
{ | |
printf("%c", p[i]); | |
} | |
} | |
printf("\n"); | |
return 0; | |
} | |
else | |
{ | |
printf("Usage: ./caesar k\n"); | |
return 1; | |
} | |
} |
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