题解 | #阿拉伯数字转中文#

package main

import (
	"strings"
	"strconv"
)

func num2cn(n int) string {
	if n == 0 {
		return "零"
	}

	negative := false
	if n < 0 {
		negative = true
		n = -n
	}

	ans := ""
	// 亿
	if n >= 100000000 {
		x := n / 100000000
		ans = ans + thousandNum2Cn(x) + "亿"
	}
	if len(ans) != 0 && n%100000000 != 0 {
		bytes := []byte(strconv.Itoa(n))
		if i := len(bytes) - 8; i >= 0 && i < len(bytes)-4 {
			if bytes[i] == '0' {
				ans += "零"
			}
		}
	}
	n %= 100000000

	// 万
	if n >= 10000 {
		x := n / 10000
		ans = ans + thousandNum2Cn(x) + "万"
	}
	if len(ans) != 0 && n%10000 != 0 {
		bytes := []byte(strconv.Itoa(n))
		if i := len(bytes) - 4; i >= 0 && i < len(bytes) {
			if bytes[i] == '0' {
				ans += "零"
			}
		}
	}
	n %= 10000

	thousand := thousandNum2Cn(n)
	if thousand != "零" {
		ans = ans + thousand
	}

	if negative {
		ans = "负" + ans
	}
	return ans
}

func thousandNum2Cn(n int) string {
	if n == 0 {
		return "零"
	}
	
	ans := ""
	numStr := []string{"零", "一", "二", "三", "四", "五", "六", "七", "八", "九"}
	units := []string{"", "十", "百", "千"}
	unit := 0
	for n > 0 {
		x := n % 10
		if x == 0 {
			if !strings.HasPrefix(ans, numStr[0]) { // 中间多个零的略去
				ans = numStr[0] + ans
			}
		} else {
			ans = numStr[x] + units[unit] + ans
		}
		n /= 10
		unit++
	}
	if strings.HasPrefix(ans, "一十") {
		ans = strings.Replace(ans, "一十", "十", 1)
	}
	if strings.HasSuffix(ans, "零") {
		ans = strings.TrimSuffix(ans, "零")
	}
	return ans
}

TODO