32 lines
978 B
C
32 lines
978 B
C
#include <stdbool.h>
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#include <stdio.h>
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char lowercase(char c) {
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// Lowercase only ASCII uppercase chars.
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if (c >= 65 && c <= 90) { return c + 32; }
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return c;
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}
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bool is_symbol_char(char c) {
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// Catch chars that precede or follow alpha chars.
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if (c < 65 || c > 122) { return true; }
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// Catch chars intervening the upper and lowercase alpha chars.
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if (c > 90 && c < 97) { return true; }
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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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// There are 26 lowercased ASCII alpha chars (97-122).
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// We can use 26 indexes to keep track of each one.
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char char_map[26] = { 0 };
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for (int i = 0; i < length(phrase); i++) {
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if (is_symbol_char(phrase[i])) { continue; } // Ignore non-alpha chars.
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if (char_map[lowercase(phrase[i]) - 97] != 0) { return false; }
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// Increment the count for this char.
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char_map[lowercase(phrase[i]) - 97]++;
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}
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return true;
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}
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