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  1. #include <stdio.h>
  2. #include <string.h>
  3. #include <ctype.h>
  4.  
  5. int main(void) {
  6. 	int n;
  7. 	scanf("%d", &n);
  8. 	char table[1001][201];
  9. 	int min_len = 201;
  10. 	for(int i=0; i<n; i++){
  11. 		scanf("%s", table[i]);
  12. 		if(strlen(table[i]) < min_len){
  13. 			min_len = strlen(table[i]);
  14. 		}
  15. 	}
  16. 	char ciphertext[10001];
  17. 	scanf(" %[^\n]", ciphertext);
  18.  
  19. 	int len_key = 0;
  20. 	char key[201];
  21. 	for(int i = 0; i < min_len; i++){
  22. 		char c = table[0][i];
  23. 		int iskey = 1;
  24. 		for(int j = 1; j < n; j++){
  25. 			if(table[j][i] != c)
  26. 				iskey = 0;
  27. 		}
  28. 		if(iskey){
  29. 			key[len_key++] = c;
  30. 		}
  31. 		else{
  32. 			break;
  33. 		}
  34. 	}
  35. 	if(len_key == 0){
  36. 		printf("\n\n");
  37. 		return 0;
  38. 	}
  39. 	else{
  40. 		key[len_key] = '\0';
  41. 		printf("%s", key);
  42. 	}
  43.  
  44. 	// decrypt
  45. 	char plaintext[10001];
  46. 	int key_i = 0;
  47. 	for(int i=0; i<strlen(ciphertext); i++){
  48. 		char k = tolower(key[key_i % len_key]) - 'a';
  49. 		char c = ciphertext[i] ;
  50. 		if(isupper(c)){
  51. 			plaintext[i] = ((ciphertext[i] - 'A') - k + 26) % 26 + 'A';
  52. 		}
  53. 		else{
  54. 			plaintext[i] = ((ciphertext[i] - 'a') - k + 26) % 26 + 'a';
  55. 		}
  56. 	}
  57. 	plaintext[strlen(ciphertext)] = '\0';
  58. 	printf("%s", plaintext);
  59.  
  60. 	return 0;
  61. }
  62.  
Success #stdin #stdout 0.01s 5320KB
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3
flower
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https://ideone.com/MdfS4E
language:
C (gcc 8.3)
created:
9 days ago
visibility:
public

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