add new solutions

solutions/4/q401/solution.go

@@ -0,0 +1,45 @@
+package q401
+
+import "fmt"
+
+func bin2time(leds []uint8) (string, bool) {
+	hour := leds[0]<<3 + leds[1]<<2 + leds[2]<<1 + leds[3]
+	minute := leds[4]<<5 +
+		leds[5]<<4 +
+		leds[6]<<3 +
+		leds[7]<<2 +
+		leds[8]<<1 +
+		leds[9]
+	if hour >= 12 || minute >= 60 {
+		return "", false
+	}
+	return fmt.Sprintf("%d:%02d", hour, minute), true
+}
+
+func iterate(remaining, offset int, leds []uint8, ret *[]string) {
+	if 10-offset < remaining {
+		return
+	}
+	if remaining == 0 {
+		if r, ok := bin2time(leds); ok {
+			*ret = append(*ret, r)
+		}
+		return
+	}
+
+	leds[offset] = 1
+	iterate(remaining-1, offset+1, leds, ret)
+	leds[offset] = 0
+	iterate(remaining, offset+1, leds, ret)
+}
+
+func readBinaryWatch(turnedOn int) []string {
+	if turnedOn >= 9 {
+		return nil
+	}
+	ret := []string{}
+	iterate(turnedOn, 0, make([]uint8, 10), &ret)
+	return ret
+}
+
+var _ = readBinaryWatch

solutions/4/q445/solution.go

@@ -0,0 +1,45 @@
+package q445
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+	var a1, a2 []*ListNode
+	for l1 != nil {
+		a1 = append(a1, l1)
+		l1 = l1.Next
+	}
+	for l2 != nil {
+		a2 = append(a2, l2)
+		l2 = l2.Next
+	}
+
+	ret := make([]ListNode, max(len(a1), len(a2))+1)
+	for i := range ret {
+		if i < len(a1) {
+			ret[i].Val += a1[len(a1)-1-i].Val
+		}
+		if i < len(a2) {
+			ret[i].Val += a2[len(a2)-1-i].Val
+		}
+		if ret[i].Val > 9 {
+			ret[i+1].Val += ret[i].Val / 10
+			ret[i].Val %= 10
+		}
+
+		if i > 0 {
+			ret[i].Next = &ret[i-1]
+		}
+	}
+
+	for i := len(ret) - 1; i >= 0; i-- {
+		if ret[i].Val > 0 {
+			return &ret[i]
+		}
+	}
+	return &ret[0]
+}
+
+var _ = addTwoNumbers