686. Repeated String Match

// LeetCode URL: https://leetcode.com/problems/repeated-string-match/
/**
 * Time Complexity: O((A + B) * B)
 *
 * A+B = Length of the new string in stringbuilder.
 *
 * Space Complexity: O(A + B)
 */
class Solution1 {
    public int repeatedStringMatch(String A, String B) {
        if (A == null || B == null) {
            return -1;
        }
        if (B.length() == 0 || B.equals(A)) {
            return 1;
        }
        if (A.length() == 0) {
            return -1;
        }

        int count = 0;
        StringBuilder sb = new StringBuilder();
        while (sb.length() < B.length()) {
            sb.append(A);
            count++;
        }

        if (sb.indexOf(B) >= 0) {
            return count;
        }

        sb.append(A);
        count++;

        if (sb.indexOf(B) >= 0) {
            return count;
        }

        return -1;
    }
}

/**
 * Using KMP for string contains.
 *
 * Time Complexity: O((A + B) + B)
 *
 * A+B = Length of the new string in stringbuilder.
 *
 * Space Complexity: O(A + B)
 */
class Solution2 {
    public int repeatedStringMatch(String A, String B) {
        if (A == null || B == null) {
            return -1;
        }
        if (B.length() == 0 || A.equals(B)) {
            return 1;
        }
        if (A.length() == 0) {
            return -1;
        }

        int count = 0;
        StringBuilder sb = new StringBuilder();
        while (sb.length() < B.length()) {
            sb.append(A);
            count++;
        }

        int[] lookupTable = kmpLookupTable(B);

        if (contains(sb.toString(), B, lookupTable)) {
            return count;
        }

        sb.append(A);
        count++;

        if (contains(sb.toString(), B, lookupTable)) {
            return count;
        }

        return -1;
    }

    private int[] kmpLookupTable(String s) {
        int[] table = new int[s.length()];
        int i = 1;
        int index = 0;
        while (i < s.length()) {
            if (s.charAt(i) == s.charAt(index)) {
                index++;
                table[i] = index;
                i++;
            } else {
                if (index > 0) {
                    index = table[index - 1];
                } else {
                    i++;
                }
            }
        }
        return table;
    }

    private boolean contains(String haystack, String needle, int[] table) {
        int i = 0;
        int j = 0;
        while (i < haystack.length() && j < needle.length()) {
            if (haystack.charAt(i) == needle.charAt(j)) {
                i++;
                j++;
            } else {
                if (j > 0) {
                    j = table[j - 1];
                } else {
                    i++;
                }
            }
        }
        if (j == needle.length()) {
            return true;
        } else {
            return false;
        }
    }
}