20201127

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
+	}
+}