Problem:
Score : 500 points

Problem Statement

Given are two strings s and t consisting of lowercase English letters. Determine if there exists an integer i satisfying the following condition, and find the minimum such i if it exists.

Let s' be the concatenation of 10^{100} copies of s. t is a subsequence of the string {s'}_1{s'}_2\ldots{s'}_i (the first i characters in s').

Notes

A subsequence of a string a is a string obtained by deleting zero or more characters from a and concatenating the remaining characters without changing the relative order. For example, the subsequences of contest include net, c, and contest.

Constraints

1 \leq |s| \leq 10^5

1 \leq |t| \leq 10^5

s and t consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

s
t

Output

If there exists an integer i satisfying the following condition, print the minimum such i; otherwise, print -1.

Sample Input 1

contest
son

Sample Output 1

10

t = son is a subsequence of the string contestcon (the first 10 characters in s' = contestcontestcontest...), so i = 10 satisfies the condition.

On the other hand, t is not a subsequence of the string contestco (the first 9 characters in s'), so i = 9 does not satisfy the condition.

Similarly, any integer less than 9 does not satisfy the condition, either. Thus, the minimum integer i satisfying the condition is 10.

Sample Input 2

contest
programming

Sample Output 2

-1

t = programming is not a substring of s' = contestcontestcontest.... Thus, there is no integer i satisfying the condition.

Sample Input 3

contest
sentence

Sample Output 3

33

Note that the answer may not fit into a 32-bit integer type, though we cannot put such a case here.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)


import java.util.*;

public class Main {

    void run() {
        Scanner sc = new Scanner(System.in);

        String s = sc.next(), t = sc.next();

        if (!exists(s, t)) {
            System.out.println(-1);
            return;
        }

        HashMap<Character, ArrayList<Integer>> map = new HashMap<>();
        HashMap<Character, Integer> lens = new HashMap<>();

        int n = s.length();
        for (int i = 0; i < n; i++) {
            ArrayList<Integer> l = map.getOrDefault(s.charAt(i), new ArrayList<>());
            l.add(i);
            map.put(s.charAt(i), l);
            lens.put(s.charAt(i), lens.getOrDefault(s.charAt(i), 0) + 1);
        }

        int m = t.length();

        long len = 0;
        int cur = 0;

        for (int i = 0; i < m; i++) {
            char c = t.charAt(i);
            ArrayList<Integer> l = map.get(c);
            int idx = lowerBound(l, cur + 1);
            if (idx == lens.get(c)) {
                len = (len / n + 1) * n;
                idx = lowerBound(l, 0);
                cur = l.get(idx);
                len += l.get(idx);

//                debug("1", l.get(idx), cur, len);
            } else {
                len += l.get(idx) - cur + 1;
                cur = l.get(idx);

//                debug("2", l.get(idx), cur, len);
            }
        }
        System.out.println(len);
    }

    boolean exists(String s, String t) {
        HashSet<Character> exists = new HashSet<>();
        int n = s.length();
        for (int i = 0; i < n; i++) exists.add(s.charAt(i));

        int m = t.length();
        for (int i = 0; i < m; i++) if (!exists.contains(t.charAt(i))) {
            return false;
        }
        return true;
    }

    public int lowerBound(ArrayList<Integer> array, int value) {
        int left = -1;
        int right = array.size();
        while (right - left > 1) {
            int middle = (right + left) / 2;
            if (array.get(middle) >= value) {
                right = middle;
            } else {
                left = middle;
            }
        }
        return right;
    }

    public int upperBound(int[] array, int value) {
        int left = -1;
        int right = array.length;
        while (right - left > 1) {
            int middle = (right + left) / 2;
            if (array[middle] > value) {
                right = middle;
            } else {
                left = middle;
            }
        }
        return right;
    }

    void debug(Object... os) {
        System.err.println(Arrays.deepToString(os));
    }

    public static void main(String[] args) {
        new Main().run();
    }

}