g0401_0500.s0459_repeated_substring_pattern.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0401_0500.s0459_repeated_substring_pattern;

// #Easy #String #String_Matching #Programming_Skills_II_Day_2
// #2022_07_19_Time_8_ms_(96.64%)_Space_51.2_MB_(47.98%)

/**
 * 459 - Repeated Substring Pattern\.
 *
 * Easy
 *
 * Given a string `s`, check if it can be constructed by taking a substring of it and appending multiple copies of the substring together.
 *
 * **Example 1:**
 *
 * **Input:** s = "abab"
 *
 * **Output:** true
 *
 * **Explanation:** It is the substring "ab" twice.
 *
 * **Example 2:**
 *
 * **Input:** s = "aba"
 *
 * **Output:** false
 *
 * **Example 3:**
 *
 * **Input:** s = "abcabcabcabc"
 *
 * **Output:** true
 *
 * **Explanation:** It is the substring "abc" four times or the substring "abcabc" twice.
 *
 * **Constraints:**
 *
 * *   1 <= s.length <= 10⁴
 * *   `s` consists of lowercase English letters.
**/
public class Solution {
    public boolean repeatedSubstringPattern(String s) {
        int n = s.length();
        if (n < 2) {
            return false;
        }
        int i = 0;
        while (i < (n + 1) / 2) {
            if (n % (i + 1) != 0) {
                i++;
                continue;
            }
            boolean match = true;
            String substring = s.substring(0, i + 1);
            int skippedI = i;
            for (int j = i + 1; j < n; j += i + 1) {
                if (!s.substring(j, j + i + 1).equals(substring)) {
                    match = false;
                    break;
                }
                skippedI += i + 1;
            }
            if (match) {
                return true;
            }
            i = skippedI;
            i++;
        }
        return false;
    }
}