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74 lines
2.2 KiB
C
74 lines
2.2 KiB
C
2 years ago
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include <float.h>
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#include "utils.h"
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// 'a'-'z', last value is a frequency of non-alphaber symbols
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const double eng_freq[] = {0.08167,0.01492,0.02782,0.04253,0.12702,0.02228,0.02015,0.06094,0.06966,0.00153,0.00772,0.04025,0.02406,0.06749,0.07507,0.01929,0.00095,0.05987,0.06327,0.09056,0.02758,0.00978,0.02360,0.00150,0.01974,0.00074,0};
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void freq(char *str, int n, double* freqs, char min, char max) {
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for (int i = 0; i < n; ++i) {
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if (str[i] >= min && str[i] <= max)
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freqs[str[i] - min]++;
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else
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freqs[max - min + 1]++;
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}
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for (int j = 0; j < max - min + 2; ++j)
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freqs[j] /= n;
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}
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double std(double *a, const double *b, int n) {
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double result = 0;
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for (int i = 0; i < n; ++i)
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result += (a[i] - b[i]) * (a[i] - b[i]);
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result /= n;
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return result;
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}
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double freq_score(char *str, int n) {
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double score = 0;
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char* str_copy = (char*)malloc(n);
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strncpy(str_copy, str, n);
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// last value is a frequency of non-alphaber symbols
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double* freqs = (double*)malloc(('z' - 'a' + 2) * sizeof(double));
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for (int i = 0; i < n; ++i)
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if (str_copy[i] >= 'A' && str_copy[i] <='Z')
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str_copy[i] = tolower(str[i]);
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freq(str_copy, n, freqs, 'a', 'z');
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score = std(freqs, eng_freq, 'z' - 'a' + 2);
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free(str_copy);
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free(freqs);
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return score;
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}
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int main() {
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char *input = (char*)malloc(34);
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read_bytes(input, 34);
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char *result = (char*)malloc(35);
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char *buf = (char*)malloc(34);
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double score = 0; double min_score = DBL_MAX;
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for (unsigned char i = 0; i < 255; ++i) {
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for (int j = 0; j < 34; ++j)
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buf[j] = input[j] ^ i;
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score = freq_score(buf, 34);
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if (score < min_score) {
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min_score = score;
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strncpy(result, buf, 34);
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}
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}
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result[34] = '\0';
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printf("%s\n", result);
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free(input); free(result); free(buf);
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}
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