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
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.

kocko: 2019-06-09 18:53:09

Quite stupid requirement for the source code size....

motormouthdoda: 2019-05-28 23:12:42

Don't use binary exponentiation. The solution is O(1)

mubasshir00: 2019-05-21 20:39:42

use Binary Exponentiation.

sahruz_riyad: 2019-05-20 14:12:36

a and b both are not zero. But separatedly can be zero.. be careful about that

Last edit: 2019-05-20 14:13:04

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