package main

import "fmt"

func multiply(num1 string, num2 string) string {
	// 1.int数组模拟存储
	len1, len2 := len(num1), len(num2)
	nums := make([]int, len1+len2, len1+len2)
	// 2.逆序移动指针，填充nus数组
	for i := len1 - 1; i >= 0; i-- {
		for j := len2 - 1; j >= 0; j-- {
			mul := int(num1[i]-'0') * int(num2[j]-'0')
			p10, p1 := mul/10, mul%10
			nums[i+j] += p10
			nums[i+j+1] += p1
			nums[i+j] += nums[i+j+1] / 10
			nums[i+j+1] %= 10
		}
	}
	// 3.过滤前导0
	idx := 0
	for idx < len(nums) && nums[idx] == 0 {
		idx++
	}
	nums = nums[idx:]
	// 3.int数组转字符串
	if len(nums) == 0 {
		return "0"
	}
	bytes := make([]byte, 0, 0)
	for _, v := range nums {
		bytes = append(bytes, byte(v+'0'))
	}
	return string(bytes)
}

func main() {
	//fmt.Println(multiply("2", "3"))
	//fmt.Println(multiply("123", "456"))
	fmt.Println(multiply("0", "0"))
}