m7013 / salestock-solution

AgeSorter, BlackListed User

salestock-solution

Lang: Java (version 1.8)

01-AgeSorter-10M-Rows

• How to produce sorted_age.txt: java AgeSorter < age.txt > sorted_age.txt

• Execution time to produce sorted_age.txt time java AgeSorter < age.txt > sorted_age.txt real 0m59.964s user 0m26.941s sys 0m32.187s

• How to generate age.txt python ageGen.py > age.txt

• Execution time to generate age.txt time python ageGen.py > age.txt real 0m19.568s user 0m19.406s sys 0m0.092s

02-AgeSorter-7B-Rows

• Solved using solution no.01 (no modification in file)
• Execution time to do sorting 7B rows: 700 * 59.964 second = ~ 11.6 hours

03-BlacklistedUser-1M-Rows

• Execution time of check_blacklist time java BlacklistChecker true real 0m1.902s user 0m4.024s sys 0m0.249s

• How to generate blacklist.txt: python genBlacklisUser.py > blacklist.txt

• Execution time to generate blacklist.txt time python genBlacklisUser.py > blacklist.txt real 0m7.346s user 0m7.268s sys 0m0.052s

Why use HashMap ?

A: In Java 8, when we have too many unequal keys which gives same hashcode(index), when the number of items in a hash bucket grows beyond certain threshold (TREEFY_THRESHOLD = 8), content of that bucket swicthes from using a 'linked list' of Entry objects to do a 'balanced tree'. This theoritically improves the worst-case performance from O(n) to O(log n). https://www.youtube.com/watch?v=c3RVW3KGIIE