Testing whether two words are anagrams

This lesson covers testing for anagrams in Objective-C, with the aim of understanding how to sort and compare strings.

An anagram is a word made by rearranging the letters of another (listen and silent, for instance). Sort the letters of both and compare.

The sample code lower-cases with lowercaseString, takes the characters one at a time into an NSMutableArray, sorts, and compares. "listen" and "silent" have the same letters, so sorted they match.

A common early stumble is not allowing for case. The sample unifies case with lowercaseString before comparing; forget that and the same word in different cases is judged different.

It is a basic technique for comparing strings while ignoring order, and it extends to simple cipher-solving games.

📖 Reference code

BOOL isAnagram(NSString *a, NSString *b) {
    NSString *lowerA = [a lowercaseString];
    NSString *lowerB = [b lowercaseString];
    NSMutableArray *charsA = [NSMutableArray array];
    NSMutableArray *charsB = [NSMutableArray array];
    for (NSUInteger i = 0; i < lowerA.length; i++) {
        [charsA addObject:[lowerA substringWithRange:NSMakeRange(i, 1)]];
    }
    for (NSUInteger i = 0; i < lowerB.length; i++) {
        [charsB addObject:[lowerB substringWithRange:NSMakeRange(i, 1)]];
    }
    NSArray *sortedA = [charsA sortedArrayUsingSelector:@selector(compare:)];
    NSArray *sortedB = [charsB sortedArrayUsingSelector:@selector(compare:)];
    return [sortedA isEqualToArray:sortedB];
}

NSLog(@"%d", isAnagram(@"listen", @"silent"));
NSLog(@"%d", isAnagram(@"hello", @"world"));

✍️ Your code

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🧪 This site can't compile or run Objective-C directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).