LeetCode:459. Repeated Substring Pattern

Posted 2020-08-30

package Today;
//LeetCode:459. Repeated Substring Pattern
/*
Given a non-empty string check if it can be constructed by taking a substring of it
and appending multiple copies of the substring together.
You may assume the given string consists of lowercase English letters only
and its length will not exceed 10000.

Example 1:
Input: "abab"
Output: True
Explanation: It‘s the substring "ab" twice.

Example 2:
Input: "aba"
Output: False

Example 3:
Input: "abcabcabcabc"
Output: True

Explanation: It‘s the substring "abc" four times. (And the substring "abcabc" twice.)
*/
public class repeatedSubstringPattern459 {
public static boolean repeatedSubstringPattern(String str) {
int len=str.length();
for(int i=0;i<len/2;i++){
if(len%(i+1)==0){
String subStr=str.substring(0, i+1);
StringBuilder sb=new StringBuilder();
for(int j=0;j<len/(i+1);j++)
sb.append(subStr);
if(sb.toString().equals(str))
return true;
}
}
return false;
}
//study abab-->abababab-->bababa去掉了一头一尾，如果是copy的，就是每一个copy向前移了一下
public static boolean repeatedSubstringPattern2(String str){
String s=str+str;
return s.substring(1,s.length()-1).contains(str);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(repeatedSubstringPattern("abab"));
System.out.println(repeatedSubstringPattern("aba"));
System.out.println(repeatedSubstringPattern("abcabcabcabc"));
System.out.println(repeatedSubstringPattern("abaababaab"));
System.out.println(repeatedSubstringPattern("ababab"));
System.out.println(repeatedSubstringPattern("aaaaaaaaaaaaa"));
System.out.println(repeatedSubstringPattern2("abab"));
System.out.println(repeatedSubstringPattern2("aba"));
System.out.println(repeatedSubstringPattern2("abcabcabcabc"));
System.out.println(repeatedSubstringPattern2("abaababaab"));
System.out.println(repeatedSubstringPattern2("ababab"));
System.out.println(repeatedSubstringPattern2("aaaaaaaaaaaaa"));
}

}