week-2019-09-08-answer.java

boolean permutation(String s, String t) {
    if (s.length() != t.length()) return false; // Permutations must be the same length

    int[] letters = new int[128]; //Assumption: ASCII
    for (int i = 0; i < s.length(); i++) {
        letters[s.charAt(i)]++;
    }
    for (int i = 0; i < t.length(); i++) {
        letters[t.charAt(i)]--;
        if (letters[t.charAt(i)] < 0) {
            return false;
        }
    }

    return true;
}