bulls-and-cows.java

/**
Two pass solution
**/

class Solution {
    public String getHint(String secret, String guess) {
        if (secret == null || guess == null || secret.length() == 0 || guess.length() == 0) {
            return "";
        }
        int len = secret.length();
        int[] map = new int[10];
        int A = 0;
        int B = 0;
        for (int i = 0; i < secret.length(); i++) {
            map[secret.charAt(i) - '0'] += 1;
        }
        
        for (int i = 0; i < guess.length(); i++) {
            char s = secret.charAt(i);
            char c = guess.charAt(i);
            if (map[c - '0'] > 0 && s == c) {
                map[c - '0'] -= 1;
                A += 1;
            }
        }
        for (int i = 0; i < guess.length(); i++) {
            char s = secret.charAt(i);
            char c = guess.charAt(i);
            if (s != c && map[c - '0'] > 0) {
                map[c - '0'] -= 1;
                B += 1;
            }
        }
        return A + "A" + B + "B";
    }
}


/**
One pass solution
**/
class Solution {
    public String getHint(String secret, String guess) {
        if (secret == null || guess == null || secret.length() == 0 || guess.length() == 0) {
            return "";
        }
        int[] map = new int[10];
        int A = 0;
        int B = 0;
        
        
        for (int i = 0; i < guess.length(); i++) {
            char s = secret.charAt(i);
            char c = guess.charAt(i);
            if (s == c) {
                A += 1;
            } else {
                if (map[s - '0'] < 0) {
                    B += 1;
                }
                if (map[c - '0'] > 0) {
                    B += 1;
                }
                map[s - '0'] += 1;
                map[c - '0'] -= 1;
            }
        }
        return A + "A" + B + "B";
    }
}