added mergesort.go

gostudent#1

mergesort.go

@@ -0,0 +1,61 @@
+package main
+
+import "fmt"
+
+func mergeSort(a []int) []int {
+
+  if len(a) <= 1 {
+    return a
+  }
+
+  left := make([]int, 0)
+  right := make([]int, 0)
+  m := len(a) / 2
+
+  for i, x := range a {
+    switch {
+    case i < m:
+      left = append(left, x)
+    case i >= m:
+      right = append(right, x)
+    }
+  }
+
+  left = mergeSort(left)
+  right = mergeSort(right)
+
+  return merge(left, right)
+}
+
+func merge(left, right []int) []int {
+
+  results := make([]int, 0)
+
+  for len(left) > 0 || len(right) > 0 {
+    if len(left) > 0 && len(right) > 0 {
+      if left[0] <= right[0] {
+        results = append(results, left[0])
+        left = left[1:len(left)]
+      } else {
+        results = append(results, right[0])
+        right = right[1:len(right)]
+      }
+    } else if len(left) > 0 {
+      results = append(results, left[0])
+      left = left[1:len(left)]
+    } else if len(right) > 0 {
+      results = append(results, right[0])
+      right = right[1:len(right)]
+    }
+  }
+
+  return results
+}
+
+func main() {
+
+  arrayzor := []int{1, 6, 2, 4, 9, 0, 5, 3, 7, 8}
+  fmt.Println("Unsorted array: ", arrayzor)
+  arrayzor = mergeSort(arrayzor)
+  fmt.Println("Sorted array: ", arrayzor)
+}