LASTDIG - The last digit

Nestor was doing the work of his math class about three days but he is tired of make operations a lot and he should deliver his task tomorrow. His math’s teacher gives him two numbers a and b. The problem consist of finding the last digit of the potency of base a and index b. Help Nestor with his problem. You are given two integer numbers: the base a (0 <= a <= 20) and the index b (0 <= b <= 2,147,483,000), a and b both are not 0. You have to find the last digit of ab.


The first line of input contains an integer t, the number of test cases (t <= 30). t test cases follow. For each test case will appear a and b separated by space.


For each test case output an integer per line representing the result.


3 10
6 2

Output: 9 6

hide comments
rikilg: 2019-07-19 15:23:43

Source limit exceeded ;-)
be careful with the digit 0
AC in 2 go's!

ghazikhan13: 2019-07-17 13:17:46

hey guys, can anyone tell me why everyone did modules division by 10 only, why not any other number ??

Last edit: 2019-07-17 14:08:23
scolar_fuad: 2019-07-09 05:46:21

Just think like Big_Mod algorithm i or find pattern you will get answer

sanket17: 2019-07-08 11:05:21

For all those who are getting WA after considering a=0,b=0 case also its due to pow() function here input is non_primitive so we cant use pow function it will not return the required value

PS: even i dont how we can know input is primitive or non primitive if somebody know pls tell me also

arphox: 2019-07-07 17:07:55

Hint: This can be done in O(1) time, just look for patterns in last digits, they will repeat somehow, somewhere :-)

imambungo: 2019-07-04 17:19:34

thanks sahruz_riyad

vurise18: 2019-06-27 11:09:29

what data type do we need to store b ?

ankyy_0103: 2019-06-22 13:40:05

My java Solution is not fitting in source code size . <(^_^)>

nagrahari: 2019-06-19 10:52:12

nice question

selfcoder24: 2019-06-12 09:31:04

use modular exponentiation with mod being 10 to fetch last digit.

Added by:Jose Daniel Rodriguez Morales
Time limit:1s
Source limit:700B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: GOSU