code kata 230826

code_kata_230826/reorder_list_test.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+)
+
+func reorderList(head *node) {
+	if head == nil || head.next == nil || head.next.next == nil {
+		return
+	}
+
+	f, s := head, head
+	for f.next != nil && f.next.next != nil {
+		f = f.next.next
+		s = s.next
+	}
+
+	sh := s.next
+	printList(sh)
+	s.next = nil
+	printList(head)
+	var pre *node
+	for sh != nil {
+		next := sh.next
+		sh.next = pre
+		pre = sh
+		sh = next
+	}
+	printList(pre)
+
+	p1, p2 := head, pre
+	for p2 != nil {
+		next1, next2 := p1.next, p2.next
+		p1.next = p2
+		p2.next = next1
+		p1, p2 = next1, next2
+	}
+	printList(head)
+}
+
+func TestReorderList(t *testing.T) {
+	printList(makeNode(10))
+	reorderList(makeNode(10))
+}
+
+func printList(head *node) {
+	for head != nil {
+		fmt.Printf("%d->", head.value)
+		head = head.next
+	}
+	fmt.Println("nil")
+}
+
+func makeNode(count int) *node {
+	var h *node = nil
+	var p *node = nil
+	for i := 0; i < count; i++ {
+		n := &node{
+			value: i,
+		}
+		if h == nil {
+			h = n
+			p = h
+		} else {
+			p.next = n
+			p = p.next
+		}
+	}
+	return h
+}
+
+type node struct {
+	value int
+	next  *node
+}