(mapreduce题) 找出有共同好友的 users --好好玩

2024年5月22日 163次阅读 来源: MapReduce

usr:friend,friend,friend…
—————

 

仅代表个人意见,希望对你帮助

 

A:B,C,D,F,E,O

B:A,C,E,K

C:F,A,D,I

D:A,E,F,L

E:B,C,D,M,L

F:A,B,C,D,E,O,M

G:A,C,D,E,F

H:A,C,D,E,O

I:A,O

J:B,O

K:A,C,D

L:D,E,F

M:E,F,G

O:A,H,I,J

 

 

最终结果：

A,B C,E 
A,C D,F 
A,D F,E 
A,F B,C,D,E,O
B,E C
C,F A,D 
D,E L
D,F A,E 
D,L E,F 
E,L D
F,M E
H,O A
I,O A

================================================

提示：

1.对于这样一个usr(A), 他的好友数list为（A:B,C,D,F,E,O） 分组如下：

 

(A B)->(A B C D F E O)

(A C)->(A B C D F E O)

(A D)->(A B C D F E O)

(A F)->(A B C D F E O)

(A E)->(A B C D F E O)

(A O->(A B C D F E O)

 

  2.假设有另一个usr(C), 她的好友数list为(C:A,B,E), 将其按照上面规则分组(注意需要compare每一个键和usr，小地放前边)：

(A C)->(A B E)

(B C)->(A B E)

(E C)->(A B E)

  3.倒排索引后，shuffle后的结果：

(A C)->(A B C D F E O)(A B E)

　4.因为(A C)的values组的个数>1 ，则我们可以很确定，一定有一组的user是A,另一组的user是C

接下来找出(A B C D F E O)(A B E)的交集(A B E)。
排除掉两个user(A C)后集合的个数>=1，因此我们可以确定(A C)有共同好友E。

 

按照此逻辑，请写出mapreduce代码：
package com.bw.hadoop;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
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;



public class GX1 {
        public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
             Configuration config = new Configuration();
             config.set("fs.defaultFS", "hdfs://192.168.0.100:9000");
             config.set("yarn.resourcemanager.hostname", "192.168.0.100");
               
           FileSystem fs = FileSystem.get(config);
                Job job = Job.getInstance(config);
             
             job.setJarByClass(GX1.class);
             
              //设置所用到的map类
              job.setMapperClass(myMapper.class);
              job.setMapOutputKeyClass(Text.class);
              job.setMapOutputValueClass(Text.class);
              
              //设置所用到的reduce类
              job.setReducerClass(myRedu.class);
              job.setOutputKeyClass(Text.class);
              job.setOutputValueClass(Text.class);
              
              //设置输入输出地址
              FileInputFormat.addInputPath(job, new Path("/input/10.txt"));
              
              Path path = new Path("/out14");
              
              //job.setPartitionerClass(myPartitioner.class);
              //job.setNumReduceTasks(2);
              
              //判断目录文件是否存在，存在的话，删除
              if(fs.exists(path)){
                  fs.delete(path, true);
              }
              //指定结果文件的输出地址
              FileOutputFormat.setOutputPath(job,path);
              
              //启动处理任务job
              boolean completion = job.waitForCompletion(true);
              if(completion){
                  System.out.println("Job SUCCESS!");
                  GX2.main(args);
              }
        }
        
        public static class myMapper extends Mapper<LongWritable, Text, Text, Text>{
            Text k=new Text();
            Text v=new Text();
            @Override
            protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)
            throws IOException, InterruptedException {
                    String line = value.toString();
                    String[] split = line.split(":");
                    String person = split[0];
                    String[] splits = split[1].split(",");
                  for(String spl:splits){
                      k.set(spl);
                      v.set(person);
                       context.write(k, v);
                  }
             }
            
            
        }
        
        public static class myRedu extends Reducer<Text, Text, Text, Text>{

            @Override
            protected void reduce(Text key, Iterable<Text> values, Reducer<Text, Text, Text, Text>.Context context)
                throws IOException, InterruptedException {
                   StringBuffer stb = new StringBuffer();
                      for(Text value:values){
                          if(stb.length()!=0){
                                 stb.append(",");
                          }
                             stb.append(value);
                       }
                          context.write(key, new Text(stb.toString()));
        
                    }        
            
            }
}
package com.bw.hadoop;

import java.io.IOException;
import java.util.Arrays;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
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;



public class GX2 {
      public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
          Configuration config = new Configuration();
          config.set("fs.defaultFS", "hdfs://192.168.0.100:9000");
           config.set("yarn.resourcemanager.hostname", "192.168.0.100");
            
            FileSystem fs = FileSystem.get(config);
              Job job = Job.getInstance(config);
           
           job.setJarByClass(GX2.class);
           
            //设置所用到的map类
            job.setMapperClass(myMapper.class);
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(Text.class);
            
            //设置所用到的reduce类
            job.setReducerClass(myRedu.class);
            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(Text.class);
            
            //设置输入输出地址
            FileInputFormat.addInputPath(job, new Path("/out14/part-r-00000"));
            
            Path path = new Path("/out15");
            
            //job.setPartitionerClass(myPartitioner.class);
            //job.setNumReduceTasks(2);
            
            //判断目录文件是否存在，存在的话，删除
            if(fs.exists(path)){
                fs.delete(path, true);
            }
            //指定结果文件的输出地址
            FileOutputFormat.setOutputPath(job,path);
            
            //启动处理任务job
            boolean completion = job.waitForCompletion(true);
            if(completion){
                System.out.println("Job SUCCESS!");
            }
      }
      
      public static class myMapper extends Mapper<LongWritable, Text, Text, Text>{

        @Override
        protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)
                throws IOException, InterruptedException {
                String line = value.toString();
                String[] split = line.split("\t");
                String friend = split[0];
                String[] persons = split[1].split(",");
                
                Arrays.sort(persons);
                
                for(int i=0; i<persons.length-2; i++){
                    for (int j=i+1; j<persons.length-1; j++){
                        context.write(new Text(persons[i]+"-"+persons[j]), new Text(friend));
                    }
                }
                
        }
          
      }
      
      public static class myRedu extends Reducer<Text, Text, Text, Text>{

        @Override
        protected void reduce(Text key, Iterable<Text> values, Reducer<Text, Text, Text, Text>.Context context)
                throws IOException, InterruptedException {
               StringBuffer stb = new StringBuffer();
               for(Text value: values){
                     stb.append(value).append(" ");
               }
               context.write(key, new Text(stb.toString()));
        }

        
                
      }
}

 



    原文作者：MapReduce
    原文地址: https://www.cnblogs.com/songhaowan/p/7239578.html
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
点赞