title: Matrix Transpose using MapReduce when there is no Row number specified
body: <p>Consider I have large input of below format</p>
  
  <p>1,2,6,4<br>
  4,5,18,7<br>
  9,1,3,5<br>
  ......</p>
  
  <p>Output should be its transpose<br>
  1 4 9 ..<br>
  2 5 1 ..<br>
  6 6 3 ..<br>
  4 7 5 ..</p>
  
  <p>In this case Row number is not specified. Column number we can get while parsing
  Assume that file is very large and will be split for multiple mappers. Since the row number is not specified, It won't be possible to identify the order of output from each mapper.
  Hence, Is it possible to pre-process the input file using another mapreduce program and provide a row number before the file being sent to the Mapper? </p>