Maximum Product of the Length of Two Palindromic Subsequences LeetCode solution in Java

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class Solution {
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  int res = 0;
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  public int maxProduct(String s) {
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    char[] strArr = s.toCharArray();
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    dfs(strArr, 0, "", "");
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    return res;
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  }
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  public void dfs(char[] strArr, int i, String s1, String s2) {
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    if (i >= strArr.length) {
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      if (isPalindromic(s1) && isPalindromic(s2)) res = Math.max(res, s1.length() * s2.length());
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      return;
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    }
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    dfs(strArr, i + 1, s1 + strArr[i], s2);
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    dfs(strArr, i + 1, s1, s2 + strArr[i]);
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    dfs(strArr, i + 1, s1, s2);
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  }
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  public boolean isPalindromic(String str) {
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    int j = str.length() - 1;
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    char[] strArr = str.toCharArray();
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    for (int i = 0; i < j; i++) {
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      if (strArr[i] != strArr[j]) return false;
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      j--;
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    }
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    return true;
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  }
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}