2018年安徽省大数据比赛MapReduce题目解答第三题-蒲公英云

2018年安徽省大数据比赛MapReduce题目解答第三题

男娘i 2023-08-17 17:48 199阅读 0赞

3、求每年最高气温（10分）

根据/opt/ahdsjjs/Temperature.txt编写MapperReduce脚本获得每年的最高气温，并输出

数据格式如下：

比如：2010012325表示在2010年01月23日的气温为25度。

现在要求使用MapReduce，计算每一年出现过的最大气温

思路：其实就是字符串的截取，那到年，以年为key进行分组，天气为value

主函数：

import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.TreeMap;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
public class Myred extends Reducer<Text, IntWritable, Text, IntWritable> {
    @Override
    protected void reduce(Text key, Iterable<IntWritable> values,
            Reducer<Text, IntWritable, Text, IntWritable>.Context context) throws IOException, InterruptedException {
        /**
         *  2014 14
            2014 16
            2014 17
            2014 10
            2014 06
         */
        int maxval = Integer.MIN_VALUE;
        int max2val = -10000000;
        for (IntWritable val : values) {        
            maxval = Math.max(maxval, val.get());
        }
        context.write(new Text(key+" "+maxval), new IntWritable(max2val));
    }
}

Map函数：

import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import tq.TQ;
public class Mymap extends Mapper<LongWritable, Text, Text, IntWritable>{
    @Override
    protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, IntWritable>.Context context)
            throws IOException, InterruptedException {
//        2014010506
//        2012010609
        String line = value.toString();
        String yera = line.substring(0,6);
        int Tem = Integer.parseInt(line.substring(8,10));
        context.write(new Text(yera), new IntWritable(Tem));
    }
}

Reduce函数：

import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.TreeMap;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
public class Myred extends Reducer<Text, IntWritable, Text, IntWritable> {
    @Override
    protected void reduce(Text key, Iterable<IntWritable> values,
            Reducer<Text, IntWritable, Text, IntWritable>.Context context) throws IOException, InterruptedException {
        /**
         *  2014 14
            2014 16
            2014 17
            2014 10
            2014 06
         */
        int maxval = Integer.MIN_VALUE;
        int max2val = -10000000;
        for (IntWritable val : values) {        
            maxval = Math.max(maxval, val.get());
        }
        context.write(new Text(key+" "+maxval), new IntWritable(max2val));
    }
}