[459. Repeated Substring Pattern] #leetcode

459_0918.java

class Solution {
  // O(n^3) O(n)
    public boolean repeatedSubstringPattern(String s) {
        int n = s.length();
        
        for (int i=1; i<=n/2; i++) {
            if (n%i == 0) {
                StringBuilder sb = new StringBuilder();
                for (int j=0; j<n/i; j++) {
                    sb.append(s.substring(0, i));
                }
                if (s.equals(sb.toString())) return true;
            }
        }
                    
        return false;
    }
}