【解題】The Decoder

ACM Volume IV 458 - The Decoder


The Problem

Write a complete program that will correctly decode a set of characters into a valid message. Your program should read a given file of a simple coded set of characters and print the exact message that the characters contain. The code key for this simple coding is a one for one character substitution based upon a single arithmetic manipulation of the printable portion of the ASCII character set.


Input and Output

For example: with the input file that contains:

1JKJ'pz'{ol'{yhklthyr'vm'{ol'Jvu{yvs'Kh{h'Jvywvyh{pvu5
1PIT'pz'h'{yhklthyr'vm'{ol'Pu{lyuh{pvuhs'I|zpulzz'Thjopul'Jvywvyh{pvu5
1KLJ'pz'{ol'{yhklthyr'vm'{ol'Kpnp{hs'Lx|pwtlu{'Jvywvyh{pvu5

your program should print the message:

*CDC is the trademark of the Control Data Corporation.
*IBM is a trademark of the International Business Machine Corporation.
*DEC is the trademark of the Digital Equipment Corporation.

Your program should accept all sets of characters that use the same encoding scheme and should print the actual message of each set of characters.


Sample Input

1JKJ'pz'{ol'{yhklthyr'vm'{ol'Jvu{yvs'Kh{h'Jvywvyh{pvu5
1PIT'pz'h'{yhklthyr'vm'{ol'Pu{lyuh{pvuhs'I|zpulzz'Thjopul'Jvywvyh{pvu5
1KLJ'pz'{ol'{yhklthyr'vm'{ol'Kpnp{hs'Lx|pwtlu{'Jvywvyh{pvu5


Sample Output

*CDC is the trademark of the Control Data Corporation.
*IBM is a trademark of the International Business Machine Corporation.
*DEC is the trademark of the Digital Equipment Corporation.


解題思考

　　這題的解法超簡單，其實只是 ASCII 碼的偏移而已。

　　只要對照題目輸出入檔的英文字部分，就可以發現每個字都差了 7 個字母(例如 input 的 'J' 到了 output 就變成了 'C')。所以只要讀入每個字元，並將其 ASCII 碼減 7 就算完成了。


參考解答(C++)

#include <iostream>

using namespace std;

int main(void)
{
    string str;

    while (getline(cin, str))
    {
        for (int i = 0; i < str.size(); i++)
        {
            cout << (char)(str[i] - 7);
        }

        cout << endl;
    }

#ifndef ONLINE_JUDGE
    system("pause");
#endif
}