54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
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#include <stdbool.h>
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#include <stdio.h>
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int length(const char string[])
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{
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int i = 0;
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while (string[i] != '\0') {
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i++;
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}
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return i+1; // Account for terminating null character.
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}
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char lowercase(char* c) {
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// Lowercase only ASCII capital characters.
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if (*c >= 65 && *c <= 90) {
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return *c + 32;
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}
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return *c;
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}
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bool is_symbol_char(char c) {
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// Ignore symbols that precede alpha chars.
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if (c < 65 || c > 122) {
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return true;
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}
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// Ignore symbols intervening the upper and lowercase chars.
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if (c > 90 && c < 97) {
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return true;
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}
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return false;
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}
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bool is_isogram(const char phrase[]) {
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if (phrase == NULL) { return false; }
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if (length(phrase) == 0) { return true; }
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// Lowercase the phrase.
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// We make a copy, since the input is constant.
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char lower_phrase[(length(phrase))];
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copy_phrase(phrase, lower_phrase);
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lowercase_phrase(lower_phrase);
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// Check if the lowercased phrase is an isogram.
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for (int i = 0; i < length(lower_phrase); i++) {
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if (is_symbol_char(lower_phrase[i])) { continue; } // Ignore non-alpha chars.
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for (int j = 0; j < length(lower_phrase); j++) {
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if (is_symbol_char(lower_phrase[j])) { continue; }
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if (j == i) { continue; }
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if (lower_phrase[i] == lower_phrase[j]) {
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return false;
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}
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}
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}
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return true;
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}
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