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#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
size_t max(int * letters, size_t n) {
int maxCount = letters[0];
int maxElementIndex = 0;
for (size_t i = 1; i < n; i++) {
if (letters[i] > maxCount) {
maxCount = letters[i];
maxElementIndex = i;
}
}
return maxElementIndex;
}
int decrypt(FILE * f) {
int c;
int letters[26] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
while ((c = fgetc(f)) != EOF) {
if (isalpha(c)) {
c = tolower(c);
c -= 'a';
letters[c] = letters[c] + 1;
}
}
size_t maxElement = max(letters, 26);
int ans;
if (maxElement >= 4) {
ans = maxElement - 4;
} else {
ans = 26 - (4 - maxElement);
}
return ans;
}
int main(int argc, char ** argv) {
if (argc != 2) {
fprintf(stderr,"Usage: breaker inputFileName\n");
return EXIT_FAILURE;
}
FILE * f = fopen(argv[1], "r");
if (f == NULL) {
perror("Could not open file");
return EXIT_FAILURE;
}
size_t key = decrypt(f);
printf("%d\n", key);
return EXIT_SUCCESS;
}
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