给定字符串，求最长回文子序列

public int longestPalindromeSubseq(String s) {
        int[][] matrix = new int[s.length()][s.length()];
        for (int i = s.length() - 1; i >= 0; i--) {
            matrix[i][i] = 1;
            for (int j = i + 1; j < s.length(); j++) {
                if (s.charAt(i) == s.charAt(j)) {
                    matrix[i][j] = matrix[i + 1][j - 1] + 2;
                } else {
                    matrix[i][j] = Math.max(matrix[i][j - 1], matrix[i + 1][j]);
                }
            }
        }
        return matrix[0][s.length() - 1];
    }