case insensitive comparison of characters

Topics

• string algorithms

bool equalIgnoreCase(char a, char b) {
    return (a == b) || (isalpha(a) && isalpha(b) && abs(a - b) == 32);
}

This method works because in ASCII:

• Uppercase letters are from 65 (‘A’) to 90 (‘Z’)
• Lowercase letters are from 97 (‘a’) to 122 (‘z’)
• The difference between same letters in different cases is always 32

Another simpler approach is to use tolower()

bool equalIgnoreCase(char a, char b) { return tolower(a) == tolower(b); }

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