459. Repeated Substring Pattern

Violence

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
class Solution {
    public boolean repeatedSubstringPattern(String s) {
        for (int length = s.length() / 2; length >= 1; length--) {
            if (s.length() % length != 0) {
                continue;
            }

            // 0 1 2 3 4 5 6 7, length = 3
            String sentinel = s.substring(0, length);
            boolean allMatch = true;
            for (int startIndex = length; allMatch && startIndex < s.length(); startIndex += length) {
                for (int i = 0, j = startIndex; j < startIndex + length; i++, j++) {
                    if (sentinel.charAt(i) != s.charAt(j)) {
                        allMatch = false;
                        break;
                    }
                }
            }

            if (allMatch) {
                return true;
            }
        }

        return false;
    }
}

Match

1
2
3
4
5
6
class Solution {
    public boolean repeatedSubstringPattern(String s) {
        String concatenated = s + s;
        return concatenated.substring(1, concatenated.length() - 1).contains(s);
    }
}

References

459. Repeated Substring Pattern