From 42fc6f545f62c2f0db5427853c8b52fc7f00fe5a Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Fri, 27 Nov 2020 09:04:10 +0800
Subject: [PATCH] 20201127

---
 20201127/main.go      |  70 ++++++++++++++++++
 20201127/main_test.go | 162 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 232 insertions(+)
 create mode 100644 20201127/main.go
 create mode 100644 20201127/main_test.go

diff --git a/20201127/main.go b/20201127/main.go
new file mode 100644
index 0000000..b3f20ed
--- /dev/null
+++ b/20201127/main.go
@@ -0,0 +1,70 @@
+package main
+
+func main() {
+
+}
+
+func hasCross(orders string) bool {
+	pm := map[[2]int]struct{}{}
+
+	current := [2]int{0, 0}
+	pm[current] = struct{}{}
+	for _, o := range orders {
+		np := nextPos(current, string(o))
+		if _, found := pm[np]; found {
+			return true
+		}
+		pm[np] = struct{}{}
+	}
+	return false
+}
+
+func nextPos(current [2]int, order string) [2]int {
+	switch order {
+	case "E":
+		current[0] += 1
+	case "S":
+		current[1] -= 1
+	case "W":
+		current[0] -= 1
+	case "N":
+		current[1] += 1
+	}
+	return current
+}
+
+func hasCross2(orders string) bool {
+	pm := map[pos]struct{}{}
+	p := &pos{0, 0}
+	pm[*p] = struct{}{}
+	for _, o := range orders {
+		p.Move(string(o))
+		if _, found := pm[*p]; found {
+			return true
+		}
+		pm[*p] = struct{}{}
+	}
+	return false
+}
+
+type pos struct {
+	x int
+	y int
+}
+
+func (p *pos) Equals(p2 *pos) bool {
+	return p.x == p2.x && p.y == p2.y
+}
+
+func (p *pos) Move(order string) {
+	switch order {
+	case "E":
+		p.x += 1
+	case "S":
+		p.y -= 1
+	case "W":
+		p.x -= 1
+	case "N":
+		p.y += 1
+	}
+}
diff --git a/20201127/main_test.go b/20201127/main_test.go
new file mode 100644
index 0000000..6bb3be9
--- /dev/null
+++ b/20201127/main_test.go
@@ -0,0 +1,162 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func Test_hasCross(t *testing.T) {
+	type args struct {
+		orders string
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			"test1",
+			args{"NES"},
+			false,
+		},
+		{
+			"test2",
+			args{"NESWW"},
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := hasCross(tt.args.orders); got != tt.want {
+				t.Errorf("hasCross() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_nextPos(t *testing.T) {
+	type args struct {
+		current [2]int
+		order   string
+	}
+	tests := []struct {
+		name string
+		args args
+		want [2]int
+	}{
+		{
+			"test_E",
+			args{[2]int{0, 0}, "E"},
+			[2]int{1, 0},
+		},
+		{
+			"test_S",
+			args{[2]int{0, 0}, "S"},
+			[2]int{0, -1},
+		},
+		{
+			"test_W",
+			args{[2]int{0, 0}, "W"},
+			[2]int{-1, 0},
+		},
+		{
+			"test_N",
+			args{[2]int{0, 0}, "N"},
+			[2]int{0, 1},
+		},
+		{
+			"test1",
+			args{[2]int{0, 0}, "N"},
+			[2]int{0, 1},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := nextPos(tt.args.current, tt.args.order); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("nextPos() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_pos_Move(t *testing.T) {
+	type fields struct {
+		x int
+		y int
+	}
+	type args struct {
+		order string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   *pos
+	}{
+		{
+			"test_E",
+			fields{0, 0},
+			args{"E"},
+			&pos{1, 0},
+		},
+		{
+			"test_S",
+			fields{0, 0},
+			args{"S"},
+			&pos{0, -1},
+		},
+		{
+			"test_W",
+			fields{0, 0},
+			args{"W"},
+			&pos{-1, 0},
+		},
+		{
+			"test_N",
+			fields{0, 0},
+			args{"N"},
+			&pos{0, 1},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			p := &pos{
+				x: tt.fields.x,
+				y: tt.fields.y,
+			}
+			p.Move(tt.args.order)
+			if !p.Equals(tt.want) {
+				t.Errorf("pos Move()=%v, want %v", p, tt.want)
+			}
+		})
+	}
+}
+
+func Test_hasCross2(t *testing.T) {
+	type args struct {
+		orders string
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			"test1",
+			args{"NES"},
+			false,
+		},
+		{
+			"test2",
+			args{"NESWW"},
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := hasCross2(tt.args.orders); got != tt.want {
+				t.Errorf("hasCross2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}