459. Repeated Substring Pattern

Version #3 九章答案TODO

Version #2 KMP之类的？懒得想了实在

Version #1 无脑分割然后append然后与原string比较
10.35 %
public class Solution {
    public boolean repeatedSubstringPattern(String s) {
        if (s == null || s.length() <= 1) return false;
        int length = s.length();
        // 0, 1, 2, 3   length = 4
        //sub = 0, 1    s.subString(0, length / 2)
        // 0, 1, 2      length = 3
        //sub = 0, 1    s.subString(0, length / 2) ... we don't care
     
        for (int end = 1; end <= length / 2; end++) {
            String sub = s.substring(0, end);
            if (isRepeated(s, sub)) return true;
        }
        return false;
    }
    private boolean isRepeated(String s, String sub) {
        int shortLength = sub.length();
        int longLength = s.length();
        if (longLength % shortLength != 0) return false;
        int multi = longLength / shortLength;
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < multi; i++) {
            sb.append(sub);
        }
        //System.out.println(sb.toString());
        return sb.toString().equals(s);
     
    }
}