A checksum is an algorithm that scans a packet of data and returns a single number. The idea is that if the packet is changed, the checksum will also change, so checksums are often used for detecting transmission errors, validating document contents, and in many other situations where it is necessary to detect undesirable changes in data.
For this problem, you will implement a checksum algorithm called Quicksum. A Quicksum packet allows only uppercase letters and spaces. It always begins and ends with an uppercase letter. Otherwise, spaces and letters can occur in any combination, including consecutive spaces.
A Quicksum is the sum of the products of each character's position in the packet times the character's value. A space has a value of zero, while letters have a value equal to their position in the alphabet. So, A=1, B=2, etc., through Z=26. Here are example Quicksum calculations for the packets "ACM" and "MID CENTRAL":
ACM: 1*1 + 2*3 + 3*13 = 46
MID CENTRAL: 1*13 + 2*9 + 3*4 + 4*0 + 5*3 + 6*5 + 7*14 + 8*20 + 9*18 + 10*1 + 11*12 = 650
Input: The input consists of one or more packets followed by a line containing only # that signals the end of the input. Each packet is on a line by itself, does not begin or end with a space, and contains from 1 to 255 characters.
Output: For each packet, output its Quicksum on a separate line in the output.
| Example Input: | Example Output: |
| ACM MID CENTRAL REGIONAL PROGRAMMING CONTEST ACN A C M ABC BBC # | 46 650 4690 49 75 14 15 |
#include<iostream>
using namespace std;
int main()
{
string s;
int sum;
while(getline(cin, s))
{
if(s == "#")
break;
sum = 0;
for(int i=0; i<s.size(); i++)
{
if(s[i] != ' ')
sum += (i+1)*(s[i]-'A'+1);
}
cout << sum << endl;
}
return 0;
}
Quicksum算法详解

本文深入介绍了Quicksum算法,一种用于数据校验的高效算法。Quicksum通过对数据包中每个字符的位置和其在字母表中的位置进行加权求和,生成一个唯一的数值,用以检测数据在传输过程中的错误。文章通过实例演示了如何计算ACM和MIDCENTRAL等数据包的Quicksum值,并提供了C++实现代码。
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