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
shantanu_25: 2020-09-17 16:57:08

I think here "a and b both are not 0" means both are not 0 at the same time.

rudra_hari007: 2020-09-15 07:33:03

Can anyone tell why normal solution is not working?

jinks: 2020-09-05 16:55:26

I'm new to SPOJ, I've submitted my solution but it crossed the memory limit of 70 bytes. How did you guys manage to solve it in less than 700 bytes?

thepankj: 2020-08-17 09:17:46

Misleading statement 'a and b both are not 0'.
Make sure you account for b = 0 in your code.

hex1729: 2020-08-14 00:24:44

No exponentiation stuff required if you use your brains in last digit patterns of powers :)
0.02 sec 9.1mb with a python code.

kishlay1105: 2020-07-26 10:25:54

calculate (a^b)mod 10 using binary exponentiation .

dungeon_mr123: 2020-07-25 17:50:47

i cannot what is mistake in code please help

gokulan_cv: 2020-07-08 10:12:01

AC After 14 Times of failed submission. Python is horrible for CP. I think I should start learning c++.

[NG] This problem can be solved in 0.00s with Python. I think you should start learning to code.

Last edit: 2020-07-08 10:18:04
acktron: 2020-06-30 12:10:36

Solved in one go using modular exponentiation four :- (a ^ n) % 10 = ( ( (a % 10) ^ n);

br0ken_c0der: 2020-06-29 07:44:07

hint: Apply fast modular exponentiation using bitmasking.

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