class Solution {
    // time O(1) because always O(26) characters
    // space O(1)
    public int findPermutationDifference(String s, String t) {
        // we cannot assume s is sorted in alphabetical order if split into
        // separate characters, so we have to build an array of their indices.
        int[] indices = new int[26];
        for (int i = 0 ; i < s.length(); i++) {
            indices[s.charAt(i) - 'a'] = i;
        }

        int sum = 0;
        for (int i = 0; i < t.length(); i++) {
            int diff = indices[t.charAt(i) - 'a'] - i;
            int absoluteDiff = diff < 0 ? -diff : diff;
            sum += absoluteDiff;
        }

        return sum;
    }
}