uva 575 Skew Binary（模拟）

When a number is expressed in decimal, the k-th digit represents a multiple of 10^k. (Digits are numbered from right to left, where the least significant digit is number 0.) For example,

When a number is expressed in binary, the k-th digit represents a multiple of 2^k. For example,

In skew binary, the k-th digit represents a multiple of 2^k+1 - 1. The only possible digits are 0 and 1, except that the least-significant nonzero digit can be a 2. For example,

The first 10 numbers in skew binary are 0, 1, 2, 10, 11, 12, 20, 100, 101, and 102. (Skew binary is useful in some applications because it is possible to add 1 with at most one carry. However, this has nothing to do with the current problem.)

Input 

The input file contains one or more lines, each of which contains an integer n. If n = 0 it signals the end of the input, and otherwise nis a nonnegative integer in skew binary.

Output 

For each number, output the decimal equivalent. The decimal value of n will be at most 2³¹ - 1 = 2147483647.

Sample Input 

10120
200000000000000000000000000000
10
1000000000000000000000000000000
11
100
11111000001110000101101102000
0

Sample Output 

44
2147483646
3
2147483647
4
7
1041110737

题目大意：根据公式求值。

解题思路：模拟公式，大水题一道。

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

int main()
{
	char str[100];

	while(1)
	{
		cin >> str;
		int n = strlen(str);

		if (n == 1 && str[0] == '0')
			break;
		
		int sum = 0;
		int t = 2;
		int a;

		do{
			a = str[n - 1] - '0';
			sum = sum + (t - 1) * a;
			t *= 2;
			n--;
		}while (n != 0);

		cout << sum << endl;
		memset(str, 0, sizeof(str));
	}
	return 0;
}