c – 项目欧拉 – 17

If the numbers 1 to 5 are written out in words: one,two,three,four,
five,then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were
written out in words,how many letters would be used?

NOTE: Do not count spaces or hyphens. For example,342 (three hundred
and forty-two) contains 23 letters and 115 (one hundred and fifteen)
contains 20 letters. The use of “and” when writing out numbers is in
compliance with British usage.

我写的代码是：

int getCount(map<int,int> numWords,int i)
{
    if (i <= 20) // one to twenty
        return numWords[i];
    else if (i <= 99 && i % 10 == 0) // thirty,forty,fifty etc.
        return numWords[i];
    else if (i <= 99) // thirty one,seventy eight etc.
    {
        int md = i % 10;
        return numWords[i-md] + numWords[md]; // (1) -> if its 55,then take 50; (2) -> take 5
    }
    else if (i <= 999 && i % 100 == 0) // two hundred,five hundred etc.
    {
        int md = i / 100;
        return numWords[md] + numWords[100]; // number + hundred
    }
    else if(i <= 999 && i % 10 == 0) // 340 three hundred forty
    {
        int hunsDig = (i - (i % 100)) / 100; // (340 - 40)/100 = 3
        int tens = i - hunsDig*100; // 340-300=40
        return numWords[hunsDig] + numWords[100] + numWords[0] + numWords[tens]; // three hundred and forty
    }
    else if(i <= 999) // 342
    {
        int hunsDig = (i - (i % 100)) / 100; // (342 - 42)/100 = 3
        int units = i % 10; // 342 % 10 = 2
        int tens = (i % 100) - units; // (342 % 100=42) - 2 = 40
        int tensCount = tens == 0 ? 0 : numWords[tens];

        return numWords[hunsDig] + numWords[100] + numWords[0] + tensCount + numWords[units]; // three hundred and forty two
    }
    else if(i==1000)
        return numWords[1] + numWords[1000];
}

void problem17()
{
    // make a map of all the words and corresponding word lengths
    map<int,int> numWords; 
    numWords[1] = 3; // one
    numWords[2] = 3; // two
    numWords[3] = 5; // three
    numWords[4] = 4; // four
    numWords[5] = 4; // five
    numWords[6] = 3; // six
    numWords[7] = 5; // seven
    numWords[8] = 5; // eight
    numWords[9] = 4; // nine
    numWords[10] = 3; // ten
    numWords[11] = 6; // eleven
    numWords[12] = 6; // twelve
    numWords[13] = 8; // thirteen
    numWords[14] = 8; // fourteen
    numWords[15] = 7; // fifteen
    numWords[16] = 7; // sixteen
    numWords[17] = 9; // seventeen
    numWords[18] = 8; // eighteen
    numWords[19] = 8; // nineteen
    numWords[20] = 6; // twenty
    numWords[30] = 6; // thirty
    numWords[40] = 5; // forty
    numWords[50] = 5; // fifty
    numWords[60] = 5; // sixty
    numWords[70] = 7; // seventy
    numWords[80] = 6; // eighty
    numWords[90] = 6; // ninety
    numWords[100] = 7; // hundred
    numWords[1000] = 8; // thousand
    numWords[0] = 3; // and

    int totalCount = 0; // total num of words

    for (int i=1; i <= 1000; i++)
    {
        totalCount += getCount(numWords,i);
    }
    cout << "Total number of letters required: " << totalCount;
}

但是,这并没有给我正确的答案.我究竟做错了什么？输出21088,答案是21124.