01: #include <iostream>
02: #include <string>
03: using namespace std;
04: /**
05:    Turn a digit into its English name
06:    @param n an integer between 1 and 9
07:    @return the name of n ("one" . . . "nine")
08: */
09: string digit_name(int n)
10: {  if (n == 1) return "one";
11:    if (n == 2) return "two";
12:    if (n == 3) return "three";
13:    if (n == 4) return "four";
14:    if (n == 5) return "five";
15:    if (n == 6) return "six";
16:    if (n == 7) return "seven";
17:    if (n == 8) return "eight";
18:    if (n == 9) return "nine";
19:    return "";
20: }
21: /**
22:    Turn a number between 10 and 19 into its English name
23:    @param n an integer between 10 and 19
24:    @return the name of n ("ten" . . . "nineteen")
25: */
26: string teen_name(int n)
27: {  if (n == 10) return "ten";
28:    if (n == 11) return "eleven";
29:    if (n == 12) return "twelve";
30:    if (n == 13) return "thirteen";
31:    if (n == 14) return "fourteen";
32:    if (n == 15) return "fifteen";
33:    if (n == 16) return "sixteen";
34:    if (n == 17) return "seventeen";
35:    if (n == 18) return "eighteen";
36:    if (n == 19) return "nineteen";
37:    return "";
38: }
39: /**
40:    Give the English name of a multiple of 10
41:    @param n an integer between 2 and 9
42:    @return the name of 10 * n ("twenty" . . . "ninety")
43: */
44: string tens_name(int n)
45: {  if (n == 2) return "twenty";
46:    if (n == 3) return "thirty";
47:    if (n == 4) return "forty";
48:    if (n == 5) return "fifty";
49:    if (n == 6) return "sixty";
50:    if (n == 7) return "seventy";
51:    if (n == 8) return "eighty";
52:    if (n == 9) return "ninety";
53:    return "";
54: }
55: /**
56:    Turn a number into its English name
57:    @param n a positive integer < 1,000,000
58:    @return the name of n (e.g. "two hundred seventy four")
59: */
60: string int_name(int n)
61: {  int c = n; /* the part that still needs to be converted */
62:    string r; /* the return value */
63: 
64:    if (c >= 1000)
65:    {  r = int_name(c / 1000) + " thousand";
66:       c = c % 1000;
67:    }
68:    if (c >= 100)
69:    {  r = r + " " + digit_name(c / 100) + " hundred";
70:       c = c % 100;
71:    }
72:    if (c >= 20)
73:    {  r = r + " " + tens_name(c / 10);
74:       c = c % 10;
75:    }
76:    if (c >= 10)
77:    {  r = r + " " + teen_name(c);
78:       c = 0;
79:    }
80:    if (c > 0)
81:       r = r + " " + digit_name(c);
82: 
83:    return r;
84: }
85: 
86: int main()
87: {  int n;
88:    cout << "Please enter a positive integer: ";
89:    cin >> n;
90:    cout << int_name(n);
91:    return 0;
92: }