下面给出一个child-parent的表格，要求挖掘其中的父子辈关系，给出祖孙辈关系的表格。

package org.apache.hadoop.examples;
import java.util.HashMap;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class C_findParents {
	public static Integer numsum = new Integer(0);
	public static Map<Text,List<Text>> levelmap=new HashMap<Text,List<Text>>();
	public C_findParents() {
	}

	public static void main(String[] args) throws Exception {
		Configuration conf = new Configuration();
		conf.set("fs.defaultFS", "hdfs://localhost:9000");
		String[] otherArgs = new String[]{"input","output"};
		if(otherArgs.length < 2) {
			System.err.println("Usage: wordcount <in> [<in>...] <out>");
			System.exit(2);
		}

		Job job = Job.getInstance(conf, "sort");
		job.setJarByClass(C_findParents.class);
		job.setMapperClass(C_findParents.TokenizerMapper.class);
		job.setMapOutputKeyClass(Text.class);
		job.setMapOutputValueClass(Text.class);
		job.setReducerClass(C_findParents.IntSumReducer.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(Text.class);

		for(int i = 0; i < otherArgs.length - 1; ++i) {
			FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
		}

		FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1]));
		System.exit(job.waitForCompletion(true)?0:1);
	}

	public static class IntSumReducer extends Reducer<Text, Text, Text, Text> {
		protected void reduce(Text key, Iterable<Text> values, Reducer<Text, Text, Text, Text>.Context context)
				throws IOException, InterruptedException {
			List<String> yeyelist = new ArrayList<String>();
			List<String> children = new ArrayList<String>();
			for(Text val:values){
				if(val.toString().endsWith("_1")){
					yeyelist.add(val.toString());
				}else if(val.toString().endsWith("_2")){
					children.add(val.toString());
				}
			}
			for(String child:children){
				for(String yeye:yeyelist){
					context.write(new Text(child.substring(0, child.length()-2)), new Text(yeye.substring(0, yeye.length()-2)));
				}
			}
		}
	}


	public static class TokenizerMapper extends Mapper<LongWritable, Text, Text, Text> {
		public TokenizerMapper() {
		}

		protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)
				throws IOException, InterruptedException {
			String line = value.toString();
			String[] values = line.split(" ");
			context.write(new Text(values[0]), new Text(values[1]+"_1"));
			context.write(new Text(values[1]), new Text(values[0]+"_2"));
		}
	}
}