solved problem 17 in cpp

cpp/Problem017_NumberLetterCounts.cpp

@@ -0,0 +1,39 @@
+#include <iostream>
+#include <string>
+using std::cout;
+
+std::string numberToString(int n) 
+{
+    if (n >= 1000) // only works for numbers below 1000
+        throw std::invalid_argument("n must be betweeen 1 and 999");
+
+    std::string firsts[] = {"", "one", "two", "three", "four", "five", "six", "zeven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
+    std::string tens[] = {"", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};
+    std::string value = "";
+
+    if (n > 99) // Hunderds
+    { 
+        value += firsts[n / 100] + "hundred";
+        n %= 100;
+        if (n > 0) { value += "and"; } // if there is text after the hundered it requires "and"
+    }
+    if (n < 20) { return value + firsts[n]; } // special cases
+    if (n < 100) // any number below 100 that is not special
+    { 
+        value += tens[n / 10];
+        value += firsts[n % 10];
+    }
+
+    return value;
+}
+
+int main()
+{
+    int sum = 0;
+    for (int i=1; i<1000; i++)
+        sum += numberToString(i).length();
+
+    sum += std::string("oneThousand").length();
+    cout << sum << "\n";    
+    return 0;
+}