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  1. #include <ctype.h>
  2. #include <stdio.h>
  3.  
  4. char g_table[25];	// 暗号表
  5. int g_reverse[26];	// 逆変換テーブル
  6.  
  7. char get_table(int x, int y)
  8. {
  9. 	if (x >= 5) x -= 5;
  10. 	if (y >= 5) y -= 5;
  11. 	return g_table[y * 5 + x];
  12. }
  13.  
  14. int main()
  15. {
  16. 	char keyword[] = "Playfair";
  17. 	char message[] = "Abandon hope, all ye who enter here.";
  18. 	char alphabet[] = "ABCDEFGHIKLMNOPQRSTUVWXYZ";
  19. 	char plaintext[100];	// 平文
  20. 	char *p, c, c1, c2;
  21. 	int i, pos, x1, y1, x2, y2;
  22.  
  23. 	// 暗号表の作成
  24. 	pos = 0;
  25. 	for (p = keyword; c = toupper(*p); p++) {
  26. 		for (i = 0; i < pos; i++) {
  27. 			if (g_table[i] == c) break;
  28. 		}
  29. 		if (i == pos) g_table[pos++] = c;
  30. 	}
  31. 	for (p = alphabet; c = *p; p++) {
  32. 		for (i = 0; i < pos; i++) {
  33. 			if (g_table[i] == c) break;
  34. 		}
  35. 		if (i == pos) g_table[pos++] = c;
  36. 	}
  37.  
  38. 	// 暗号表の表示
  39. 	for (i = 0; i < 25; i++) {
  40. 		printf("%c%c", g_table[i], ((i+1)%5) ? ' ' : '\n');
  41. 	}
  42.  
  43. 	// 逆変換テーブルの作成
  44. 	for (i = 0; i < 25; i++) {
  45. 		c = g_table[i] - 'A';
  46. 		g_reverse[c] = i;
  47. 	}
  48. 	g_reverse[9] = g_reverse[8];	// J <- I
  49.  
  50. 	// 逆変換テーブルの表示
  51. 	for (i = 0; i < 26; i++) {
  52. //		printf("%c:%d\n", 'A'+i, g_reverse[i]);
  53. 	}
  54.  
  55. 	// メッセージを加工
  56. 	pos = 0;
  57. 	for (p = message; c = *p; p++) {
  58. 		if (!isalpha(c)) continue;
  59. 		if (pos > 0 && plaintext[pos-1] == c) {
  60. 			plaintext[pos++] = 'x';
  61. 		}
  62. 		plaintext[pos++] = c;
  63. 	}
  64. 	if (pos & 1) plaintext[pos++] = 'x';
  65. 	plaintext[pos] = '\0';
  66.  
  67. 	printf("[%s]\n", plaintext);
  68.  
  69. 	// 暗号化
  70. 	for (p = plaintext; *p; ) {
  71. 		pos = g_reverse[toupper(*p++) - 'A'];
  72. 		x1 = pos % 5;
  73. 		y1 = pos / 5;
  74. 		pos = g_reverse[toupper(*p++) - 'A'];
  75. 		x2 = pos % 5;
  76. 		y2 = pos / 5;
  77. 		if (x1 == x2) {
  78. 			// 同じ列の場合
  79. 			c1 = get_table(x1, y1 + 1);
  80. 			c2 = get_table(x2, y2 + 1);
  81. 		} else if (y1 == y2) {
  82. 			// 同じ行の場合
  83. 			c1 = get_table(x1 + 1, y1);
  84. 			c2 = get_table(x2 + 1, y2);
  85. 		} else {
  86. 			// 行も列も違う場合
  87. 			c1 = get_table(x2, y1);
  88. 			c2 = get_table(x1, y2);
  89. 		}
  90. 		printf("%c%c ", c1, c2);
  91. 	}
  92. 	printf("\n");
  93.  
  94. 	return 0;
  95. }
  96.  
Success #stdin #stdout 0.01s 1676KB
comments (?)
stdin
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Standard input is empty
stdout
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P L A Y F
I R B C D
E G H K M
N O Q S T
U V W X Z
[Abandonhopealxlyewhoenterherex]
BH PQ RT QE NL HP YV AF HU GQ NU NM BG GI KU
https://ideone.com/A4gq7
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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