Add solution to Project Euler Problem 016

src/project_euler/ProjectEuler.jl

@@ -20,6 +20,7 @@ export problem_012
 export problem_013
 export problem_014
 export problem_015
+export problem_016
 
 include("../math/divisors.jl")
 include("../math/sieve_of_eratosthenes.jl")
@@ -38,5 +39,6 @@ include("problem_012.jl")
 include("problem_013.jl")
 include("problem_014.jl")
 include("problem_015.jl")
+include("problem_016.jl")
 
 end

src/project_euler/problem_016.jl

@@ -0,0 +1,28 @@
+"""
+    Power Digit Sum
+
+2^15 = 32768 and the sum of its digits is 3+2+7+6+8=26.
+What is the sum of the digits of the number 2^1000?
+grid?
+
+# Input parameters:
+- `a` : base
+- `n` : exponent
+
+# Examples/Tests:
+```julia
+problem_016(1, 1)       # returns 1
+problem_016(2, 15)      # returns 26
+problem_016(2, 1000)    # returns 1366
+problem_016(2, -4)      # throws DomainError
+```
+
+# Reference
+- https://projecteuler.net/problem=15
+
+Contributed by: [Praneeth Jain](https://www.github.com/PraneethJain)
+"""
+function problem_016(a::T, n::T) where {T<:Integer}
+    (a <= 0 || n <= 0) && throw(DomainError("a and n must be greater than 1"))
+    return sum(parse(Int, digit) for digit in string(big(a)^n))
+end

test/project_euler.jl

@@ -91,4 +91,11 @@ using TheAlgorithms.ProjectEuler
         @test_throws DomainError problem_015(0, 5)
         @test_throws DomainError problem_015(-3, 0)
     end
+
+    @testset "Project Euler: Problem 016" begin
+        @test problem_016(1, 1) == 1
+        @test problem_016(2, 15) == 26
+        @test problem_016(2, 1000) == 1366
+        @test_throws DomainError problem_016(2, -4)
+    end
 end