add new solutions

solutions/0/q43/solution.go

@@ -0,0 +1,49 @@
+package q43
+
+import "slices"
+
+func multiply(num1, num2 string) string {
+	if num1 == "0" || num2 == "0" {
+		return "0"
+	}
+
+	l1, l2 := len(num1), len(num2)
+	res := make([]byte, l1+l2)
+
+	// Calculation
+	for i1 := range l1 {
+		n1 := num1[l1-1-i1] - '0'
+		if n1 == 0 {
+			continue
+		}
+		for i2 := range l2 {
+			n2 := num2[l2-1-i2] - '0'
+			j := i1 + i2
+			res[j] += n1 * n2
+			if res[j] > 9 {
+				res[j+1] += res[j] / 10
+				res[j] = res[j] % 10
+			}
+		}
+		for i := l2 + i1; res[i] > 9; i++ {
+			res[i+1] += res[i] / 10
+			res[i] = res[i] % 10
+		}
+	}
+
+	// Post process
+	for i := len(res) - 1; i >= 0; i-- {
+		if res[i] > 0 {
+			res = res[:i+1]
+			break
+		}
+	}
+
+	slices.Reverse(res)
+	for i := range res {
+		res[i] = res[i] + '0'
+	}
+	return string(res)
+}
+
+var _ = multiply