init

LICENSE

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+MIT License
+Copyright (c) 2018 Stephen McQuay
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# smerge
+
+This answers an interview question

main.go

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+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"sort"
+	"sync"
+	"time"
+)
+
+func main() {
+	for i := range merge(source(5), source(10), source(20)) {
+		fmt.Printf("%20d\n", i)
+	}
+}
+
+func source(c int) <-chan int {
+	out := make(chan int)
+	go func() {
+		vals := make([]int, c)
+		src := rand.New(rand.NewSource(time.Now().UnixNano()))
+		for i := 0; i < c; i++ {
+			vals[i] = src.Int()
+		}
+
+		sort.Ints(vals)
+
+		for _, i := range vals {
+			out <- i
+		}
+		close(out)
+	}()
+	return out
+}
+
+func merge(cs ...<-chan int) <-chan int {
+	wg := sync.WaitGroup{}
+	out := make(chan int)
+
+	output := func(c <-chan int) {
+		for n := range c {
+			out <- n
+		}
+		wg.Done()
+	}
+
+	wg.Add(len(cs))
+	for _, c := range cs {
+		go output(c)
+	}
+	go func() {
+		wg.Wait()
+		close(out)
+	}()
+	return out
+}