100_Days_of_LeetCode/Day_44.java at main · vanshcoder99/100_Days_of_LeetCode · GitHub

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// Longest Happy Prefix
class Solution {
    public String longestPrefix(String s) {
        int n = s.length();
        int[] lps = new int[n];
        int len = 0, i = 1;
        while(i<n){
            if(s.charAt(len) == s.charAt(i)){
                len++;
                lps[i] = len;
                i++;
            }
            else{
                if(len != 0){
                    len = lps[len-1];
                }
                else{
                    lps[i] = 0;
                    i++;
                }
            }
        }
        return s.substring(0,lps[n-1]);
    }
}


// Repeated Substring Pattern
class Solution {
    public boolean repeatedSubstringPattern(String s) {
        int n = s.length();
        int[] lps = new int[n];
        int len = 0, i = 1;
        while(i<n){
            if(s.charAt(len) == s.charAt(i)){
                len++;
                lps[i] = len;
                i++;
            }
            else{
                if(len != 0){
                    len = lps[len-1];
                }
                else{
                    lps[i] = 0;
                    i++;
                }
            }
        }
        int rlen = n - lps[n-1];
        if(rlen == n) return false;
        return (n % rlen == 0) ? true : false;
    }
}