Coding Life

It is a well-known fact that behind every good comet is a UFO. These UFOs often come to collect loyal supporters from here on Earth. Unfortunately, they only have room to pick up one group of followers on each trip. They do, however, let the groups know ahead of time which will be picked up for each comet by a clever scheme: they pick a name for the comet which, along with the name of the group, can be used to determine if it is a particular group's turn to go (who do you think names the comets?). The details of the matching scheme are given below; your job is to write a program which takes the names of a group and a comet and then determines whether the group should go with the UFO behind that comet.

Both the name of the group and the name of the comet are converted into a number in the following manner: the final number is just the product of all the letters in the name, where "A" is 1 and "Z" is 26. For instance, the group "USACO" would be 21 * 19 * 1 * 3 * 15 = 17955. If the group's number mod 47 is the same as the comet's number mod 47, then you need to tell the group to get ready! (Remember that "a mod b" is the remainder left over after dividing a by b; 34 mod 10 is 4.)

Write a program which reads in the name of the comet and the name of the group and figures out whether according to the above scheme the names are a match, printing "GO" if they match and "STAY" if not. The names of the groups and the comets will be a string of capital letters with no spaces or punctuation, up to 6 characters long.

Examples:

Input	Output
COMETQ HVNGAT	GO
ABSTAR USACO	STAY

PROGRAM NAME: ride

INPUT FORMAT

Line 1:	An upper case character string of length 1..6 that is the name of the comet.
Line 2:	An upper case character string of length 1..6 that is the name of the group.

NOTE: The input file has a newline at the end of each line but does not have a "return". Sometimes, programmers code for the Windows paradigm of "return" followed by "newline"; don't do that! Use simple input routines like "readln" (for Pascal) and, for C/C++, "fscanf" and "fid>>string".

SAMPLE INPUT (file ride.in)

COMETQ

HVNGAT

 

OUTPUT FORMAT

A single line containing either the word "GO" or the word "STAY".

 

SAMPLE OUTPUT (file ride.out)

GO

  

我的解答：

题目假设A=1, B=2, …, Z=26，将一个字符串的每个字符代表的值相乘得到的值再对47取模后的值就是一个所谓的“final number”。题目的要求是分别计算给出的两个字符串的“final number”，如果这个“final number”相同，则输出“GO”，否则输出“STAY”。

这个是一个简单的模拟题，主要算法是分解字符并计算其代表的值。这些都可以用解析的方法得到。

#include <fstream>
using namespace std;

int main(void)
{
    ofstream fout("ride.out");
    ifstream fin("ride.in");
    int scheme(char*);
    char a[10], b[10];
    fin >> a >> b;
    if (scheme(a) == scheme(b))
        fout << "GO" << endl;
    else
        fout << "STAY" << endl;
    return 0;    
}

int scheme(char* str)
{
    int num = 1, len = strlen(str);
    for (int i = 0; i < len; i++)
        num *= str[i] - 'A' + 1;
    return (num % 47);
}

官方答案：

Analysis: Your Ride Is Here

This is probably the easiest problem in the entire set of lessons. An `ad hoc' problem, no particular algorithms or tricks are needed save one: one must be careful to get all 72 characters of input without processing the newline on the end!

Here is a prototype solution:

#include <stdio.h>
#include <ctype.h>

int hash(char *s)
{
    int i, h;

    h = 1;
    for(i=0; s[i] && isalpha(s[i]); i++)
        h = ((s[i]-'A'+1)*h) % 47;
    return h;
}

void main(void)
{
    FILE *in, *out;
    char comet[100], group[100];  /**//* bigger than necessary, room for newline */

    in = fopen("input.txt", "r");
    out = fopen("output.txt", "w");

    fgets(comet, sizeof comet, in);
    fgets(group, sizeof group, in);

    if(hash(comet) == hash(group))
        fprintf(out, "GO\n");
    else
        fprintf(out, "STAY\n");
    exit (0);
}

 Solutions generally run in under 0.01 seconds.