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84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
/*
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Restriction: Input string has to be in lower case without any special characters
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*/
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#include <stdio.h>
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#include <string.h>
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void mul(int first[3][3], int second[3][10], int result[3][10])
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{
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int c, d, sum, k;
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int i, j;
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for ( c = 0 ; c < 3 ; c++ )
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{
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for ( d = 0 ; d < 10 ; d++ )
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{
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sum = 0;
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for ( k = 0 ; k < 3 ; k++ )
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{
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sum = sum + first[c][k] * second[k][d];
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}
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result[c][d] = sum;
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}
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}
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}
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int main()
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{
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char str[29] = "this message is to be encoded";
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int len;
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int i, j;
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int result[3][10] = {0};
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int key[3][3] =
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{
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{-3, -3, -4},
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{0, 1, 1},
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{4, 3, 4}
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};
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int inv_key[3][3] =
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{
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{1, 0, 1},
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{4, 4, 3},
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{-4, -3, -3}
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};
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int encode[3][10] = {32};
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int decode[3][10] = {0};
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len = strlen(str);
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for (i = 0; i < 10; i++)
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{
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for(j = 0; j < 3; j++)
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{
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if (str[j + i*3] >='a' && str[j + i*3] <='z')
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{
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encode[j][i] = str[j + i*3] - 96;
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}
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if (str[j + i*3] == 32)
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{
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encode[j][i] = 32;
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}
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if (str[j + i*3] == '\0')
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break;
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}
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if (str[j + i*3] == '\0')
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break;
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}
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mul( key, encode, result);
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printf("\nEncoded message to be sent: ");
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for (i = 0; i < 10; i++)
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{
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for ( j = 0 ; j < 3; j++)
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printf("%d, ", result[j][i]);
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}
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printf("\nDecoded message is: ");
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mul(inv_key, result, decode);
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for (i = 0; i < 10; i++)
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{
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for ( j = 0; j < 3; j++)
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{
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if ( ((decode[j][i]+96)) >= 97 && ((decode[j][i]+96) <= 123))
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printf("%c", (decode[j][i] + 96) );
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else if ( decode[j][i] == 32)
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printf(" ");
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else
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return;
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}
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}
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return 0;
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} |