import java.util.*;
 
class Ideone {
	public static void main (String[] args)	{
        String seq1 = "TTCGATGGAGCTGTA";
        String seq2 = "TAGCTAGCTCGGCATGA";
        System.out.println(count_mismatches(seq1, seq2));
    }
 
    public static int count_mismatches(String seq1, String seq2) {
        Map<Character, Character> pairs = Map.of('A', 'T', 'T', 'A', 'G', 'C', 'C', 'G');
        int count = 0;
        for (int i = 0; i < Math.min(seq1.length(), seq2.length()); i++) {
            if (pairs.get(seq1.charAt(i)) == seq2.charAt(i)) {
                count++;
            }
        }
        return Math.max(seq1.length(), seq2.length()) - count;
    }
 
}

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