Problem 17 Number letter counts （统计字母）

Number letter counts

Problem 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.

Answer: 21124 Completed on Thu, 27 Oct 2016, 05:16

题解：从1算到100，再从100 算到1000.

代码：

#include <bits/stdc++.h>
using namespace std;
int main()
{
//1-9
int s1[] = { 0, 3, 3, 5, 4, 4, 3, 5, 5, 4 };
//10-19
int s2[] = { 3, 6, 6, 8, 8, 7, 7, 9, 8, 8 };
//20 30 40 50 60 70 80 90
int s3[] = { 0, 0, 6, 6, 5, 5, 5, 7, 6, 6 };

int hundred = 7;
int And = 3;
int thousand = 8;

int i;
int sum = 0;

//1-9
for (i = 1; i < 10; i++)
{
sum += s1[i];
}

//10-19
for (i = 0; i < 10; i++){
sum += s2[i];
}

//20-99
for (i = 20; i < 100; i++){
sum += s3[i/10] + s1[i%10];
}

//100-999
for (i = 1; i < 10; i++)
{
int j;
//计算hundred
sum += s1[i] + hundred;
// i*100 + j
for (j = 1; j < 10; j++){
sum += s1[i] + hundred + And + s1[j];
}
//i*100 + j*10
for (j = 0; j < 10; j++) {
sum += s1[i] + hundred + And + s2[j];
}
//i*100 +j*10 +k
for (j = 20; j < 100; j++) {
sum += s1[i] + hundred + And + s3[j/10] + s1[j%10];
}
}

//1000
sum += 3 + thousand;

cout<<sum<<endl;
return 0;
}