CareerCup 150

C.C 1.3

/**
 * 1.3 Given two strings, write a method to decide if one is a permutation of
 * the other.
 *
 * @author Jiateng
 */
public class CC1_3 {
 
    //Time O(n), Space O(1)
    public static boolean permutation(String s1, String s2) {

        //null should be check first
        if (s1 == null || s2 == null) {
            return false;
        }
        if (s1.isEmpty() && s2.isEmpty()) {
            return true;
        }
        if (s1.isEmpty() || s2.isEmpty()) {
            return false;
        }
        if (s1.length() != s2.length()) {
            return false;
        }

        int[] array = new int[256];
        //char to int, ASCII
        for (char c : s1.toCharArray()) {
            //System.out.println(c);
            //System.out.println(Integer.valueOf(c));
            array[c] += 1;
        }
        //if s1 is equal to s2, all in array will be 0
        for (char c : s2.toCharArray()) {
            array[c] -= 1;
        }

        for (int i : array) {
            if (i != 0) {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        System.out.println(permutation("", ""));
        System.out.println(permutation("abc", "cba"));
        System.out.println(permutation("asf", ""));
        System.out.println(permutation(null, "asf"));
    }
}