match or compare 2 columns to distinguish duplicate data

I have spent so much time trying to resolve this, and help is much appreciated.

I have attached a spreadsheet where I have some same and some different data in column a and columnb. I need to sort the data so I can see the same value on the same row.

E.G. I have the below extract:

Party Number Party Number 2
500012281 500021685
500016910 500009119
500021685 500012281

I need it to show as the below to identify the same data in each column

Party Number Party Number 2
500012281 500012281
500016910
500021685 500021685

Here I can see that column2 has two entries that are duplicated in column1, and one entry that has duplicate. Is there a way of soriting and arranging this data?