add new solutions

solutions/2/q202/solution.go

@@ -0,0 +1,29 @@
+package q202
+
+type void struct{}
+
+func next(n int) int {
+	ret := 0
+	for n > 0 {
+		digit := n % 10
+		n /= 10
+		ret += digit * digit
+	}
+	return ret
+}
+
+func isHappy(n int) bool {
+	seen := map[int]void{n: {}}
+	for {
+		n = next(n)
+		if n == 1 {
+			return true
+		}
+		if _, ok := seen[n]; ok {
+			return false
+		}
+		seen[n] = void{}
+	}
+}
+
+var _ = isHappy