leetcode 273: Integer to English Words

最新推荐文章于 2020-09-20 06:42:33 发布

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本文介绍了一种使用C++编程实现将整数转换为英文单词的方法，包括处理千位、百位、十位及个位数的情况，并且特别注意了20到99之间的特殊数字表达。

Be careful about many corner cases.

class Solution {
public:
    string numberToWords(int num) {
        string res;
        vector<string> mp(10);
        vector<string> mp1(10);
        mp[0]="";
        mp[1]="One";
        mp[2]="Two";
        mp[3]="Three";
        mp[4]="Four";
        mp[5]="Five";
        mp[6]="Six";
        mp[7]="Seven";
        mp[8]="Eight";
        mp[9]="Nine";
        mp1[2]="Twenty";
        mp1[3]="Thirty";
        mp1[4]="Forty";
        mp1[5]="Fifty";
        mp1[6]="Sixty";
        mp1[7]="Seventy";
        mp1[8]="Eighty";
        mp1[9]="Ninety";
        while(num>=100)
        {
            if(!res.empty())
                res+=" ";
            string temp;
            if(num>=1000000000)
            {
                temp=numberToWords(num/1000000000);
                res+=temp+" Billion";
                num%=1000000000;
            }
            else if(num>=1000000)
            {
                temp=numberToWords(num/1000000);
                res+=temp+" Million";
                num%=1000000;
            }
            else if(num>=1000)
            {
                temp=numberToWords(num/1000);
                res+=temp+" Thousand";
                num%=1000;
            }
            else if(num>=100)
            {
                res+=mp[num/100]+" Hundred";
                num%=100;
            }
        }
        if(!res.empty()&&num)
            res+=" ";
        if(num>=20)
        {
            int digit=num/10;
            res+=mp1[digit];
            if(num%10)
                res+=" "+mp[num%10];
        }
        else if(num>=10&&num<20)
        {
            switch(num)
            {
                case 10:
                    res+="Ten";
                    break;
                case 11:
                    res+="Eleven";
                    break;
                case 12:
                    res+="Twelve";
                    break;
                case 13:
                    res+="Thirteen";
                    break;
                case 14:
                    res+="Fourteen";
                    break;
                case 15:
                    res+="Fifteen";
                    break;
                case 16:
                    res+="Sixteen";
                    break;
                case 17:
                    res+="Seventeen";
                    break;
                case 18:
                    res+="Eighteen";
                    break;
                case 19:
                    res+="Nineteen";
                    break;
            }
        }
        else if(num>0)
        {
            res+=mp[num];
        }
        if(res.empty()&&num==0)
            res="Zero";
        return res;
    }
};