adjacent single char exchange

hive-udf-adjacent-chars-checker.java

import org.apache.hadoop.hive.ql.exec.UDF;

public class CheckSwapCharsUDF extends UDF {
    public Integer evaluate(String str1, String str2) throws Exception {
        if (str1 == null || str2 == null)
            return -1;
        int s1_len = str1.length();
        int s2_len = str2.length();
        if (s1_len != s2_len)
            return -1;
        return check(str1, str2, s1_len, s2_len);
    }

    /**
     * 判断两个长度相同的串,是否仅仅有两个相邻字符交换
     * 例如: "天安门" 和 "安天门"
     */
    public static int check(String str1, String str2, int s1_len, int s2_len) {
        if (s1_len != s2_len)
            return -1;
        int flag = 0;
        int i = 0, j =0;

        while (i < s1_len && j < s2_len) {
            if (str1.charAt(i) == str2.charAt(j)) {
                i ++;
                j ++;
            } else {
                if (flag == 1 || i + 1 >= s1_len || j + 1 >= s2_len)
                    return -1;
                if (str2.charAt(j) == str1.charAt(i+1) && str2.charAt(j+1) == str1.charAt(i)) {
                    i += 2;
                    j += 2;
                    flag = 1;
                } else
                    return -1;
            }
        }
        return 1;
    }
}