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public class Solution {
    public String getHint(String secret, String guess) {
        int[] vector = new int[10];
        int len = secret.length();
        int cntA = 0;
        int cntB = 0;
        for(int i = 0; i < len; i++) {
            char s = secret.charAt(i);
            char g = guess.charAt(i);
            if (s == g) {
                cntA++;
            } else {
                if(vector[s - '0']++ < 0) cntB++;
                if(vector[g - '0']-- > 0) cntB++;
            }
        }
        return cntA + "A" + cntB + "B";
    }
}