Step 4: Set the partition ID of each record to the largest partition ID found in step 3

step4.txt

-- Input:
source	node	partition
node
28	28	29
28	29	29
28	23	29
20	20	26
20	26	26
20	25	26
20	24	26
20	23	29
20	22	26
20	21	26

-- Group by source node:
Group for source 28:
28	28	29   <=== DO NOT INCLUDE IN ADJACENCY LIST
28	29	29
28	23	29
Group for source 20:
20	23	29
20	20	26   <=== DO NOT INCLUDE IN ADJACENCY LIST
20	26	26
20	25	26
20	24	26
20	22	26
20	21	26

-- Re-create the adjacency list using the first partition ID as partition ID:
part.	source	adjacency list
ID	node
29	28	29,23
29	20	23,26,25,24,22,21   <=== THIS ONE GOT UPDATED FROM 26 TO 29