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authorDimitri Sokolyuk <demon@dim13.org>2016-08-26 14:44:10 +0200
committerDimitri Sokolyuk <demon@dim13.org>2016-08-26 14:44:10 +0200
commitacbc22c498a5e58b810f6a3838fa85e597b7f4d9 (patch)
tree1e543f56ad4e63a0df55a5ea269b41720bb0f287
parentf47002f53090869eb8a0d725b7770959a3af30db (diff)
Solve sum of multiples
-rw-r--r--go/sum-of-multiples/README.md29
-rw-r--r--go/sum-of-multiples/sum_of_multiples.go34
-rw-r--r--go/sum-of-multiples/sum_of_multiples_test.go73
3 files changed, 136 insertions, 0 deletions
diff --git a/go/sum-of-multiples/README.md b/go/sum-of-multiples/README.md
new file mode 100644
index 0000000..621777b
--- /dev/null
+++ b/go/sum-of-multiples/README.md
@@ -0,0 +1,29 @@
+# Sum Of Multiples
+
+Write a program that, given a number, can find the sum of all the multiples of particular numbers up to but not including that number.
+
+If we list all the natural numbers up to but not including 20 that are
+multiples of either 3 or 5, we get 3, 5, 6 and 9, 10, 12, 15, and 18.
+
+The sum of these multiples is 78.
+
+Write a program that can find the sum of the multiples of a given set of
+numbers.
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+ go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://exercism.io/languages/go).
+
+## Source
+
+A variation on Problem 1 at Project Euler [http://projecteuler.net/problem=1](http://projecteuler.net/problem=1)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+
diff --git a/go/sum-of-multiples/sum_of_multiples.go b/go/sum-of-multiples/sum_of_multiples.go
new file mode 100644
index 0000000..c99cdd7
--- /dev/null
+++ b/go/sum-of-multiples/sum_of_multiples.go
@@ -0,0 +1,34 @@
+package summultiples
+
+import "sync"
+
+func MultipleSummer(n ...int) func(top int) int {
+ return func(top int) int {
+ c := make(chan int)
+ wg := sync.WaitGroup{}
+ // spawn worker
+ for _, v := range n {
+ wg.Add(1)
+ go func(m int) {
+ for i := m; i < top; i += m {
+ c <- i
+ }
+ wg.Done()
+ }(v)
+ }
+ go func() {
+ wg.Wait()
+ close(c)
+ }()
+ // collect, uniq and sum up values
+ var sum int
+ seen := make(map[int]bool)
+ for v := range c {
+ if !seen[v] {
+ seen[v] = true
+ sum += v
+ }
+ }
+ return sum
+ }
+}
diff --git a/go/sum-of-multiples/sum_of_multiples_test.go b/go/sum-of-multiples/sum_of_multiples_test.go
new file mode 100644
index 0000000..9ab0bb2
--- /dev/null
+++ b/go/sum-of-multiples/sum_of_multiples_test.go
@@ -0,0 +1,73 @@
+package summultiples
+
+import "testing"
+
+var test35 = []struct {
+ limit int
+ sum int
+}{
+ {1, 0},
+ {4, 3},
+ {10, 23},
+ {100, 2318},
+ {1000, 233168},
+}
+
+var varTests = []struct {
+ divisors []int
+ limit int
+ sum int
+}{
+ {[]int{7, 13, 17}, 20, 51},
+ {[]int{43, 47}, 10000, 2203160},
+ {[]int{5, 10, 12}, 10000, 13331672},
+ {[]int{1, 1}, 10000, 49995000},
+ // Note: The following test case deviates from the README.
+ // The README specifies some rather odd defaults, whereas
+ // this has the more logical approach of not implementing any
+ // defaults, which causes the resulting sum to be zero.
+ // See discussion in:
+ // https://github.com/exercism/xgo/issues/256 and
+ // https://github.com/exercism/x-common/issues/198
+ {[]int{}, 10000, 0},
+}
+
+func Test35(t *testing.T) {
+ sum35 := MultipleSummer(3, 5)
+ for _, test := range test35 {
+ s := sum35(test.limit)
+ if s != test.sum {
+ t.Fatalf("Sum to %d returned %d, want %d.", test.limit, s, test.sum)
+ }
+ }
+}
+
+func TestVar(t *testing.T) {
+ for _, test := range varTests {
+ sv := MultipleSummer(test.divisors...)
+ s := sv(test.limit)
+ if s != test.sum {
+ t.Fatalf("Sum of multiples of %v to %d returned %d, want %d.",
+ test.divisors, test.limit, s, test.sum)
+ }
+ }
+}
+
+func Benchmark35(b *testing.B) {
+ sum35 := MultipleSummer(3, 5)
+ b.ResetTimer() // bench just the sum function
+ for i := 0; i < b.N; i++ {
+ for _, test := range test35 {
+ sum35(test.limit)
+ }
+ }
+}
+
+func BenchmarkVar(b *testing.B) {
+ // bench combined time to bind sum function and call it.
+ for i := 0; i < b.N; i++ {
+ for _, test := range varTests {
+ MultipleSummer(test.divisors...)(test.limit)
+ }
+ }
+}