Project Euler：Problem 40 Champernowne's constant

An irrational decimal fraction is created by concatenating the positive integers:

0.123456789101112131415161718192021...

It can be seen that the 12^th digit of the fractional part is 1.

If d_n represents the n^th digit of the fractional part, find the value of the following expression.

d₁ × d₁₀ × d₁₀₀ × d₁₀₀₀ × d₁₀₀₀₀ × d₁₀₀₀₀₀ × d_1000000

#include <iostream>
#include <string>
using namespace std;

string int_str(int a)
{
	string res = "";
	while (a)
	{
		char s = a % 10 + '0';
		res = s + res;
		a /= 10;
	}
	return res;
}

int main()
{
	string s = "";
	for (int i = 1; i <= 1000000; i++)
	{
		s = s + int_str(i);
	}
	int ans = 1;
	ans = (s[1 - 1] - '0')*(s[10 - 1] - '0')*(s[100 - 1] - '0')*(s[1000 - 1] - '0')*(s[10000 - 1] - '0')*(s[100000 - 1] - '0')*(s[1000000 - 1] - '0');
	cout << ans << endl;
	system("pause");
	return 0;
}

Project Euler：Problem 40 Champernowne's constant

原文：http://blog.csdn.net/youb11/article/details/46358267