基本转换问题 [英] Base Conversion Problem

问题描述

我正在尝试将一个整数转换为字符串，我现在有一个问题。

我已经得到了代码编写和工作大部分，但它有一个小缺陷，携带到下一个地方。这很难描述，所以我给你一个例子。使用由小写字母组成的字符集的基数26：

0 =a

1 =b

2 =c

...

25 =z

26 =ba（这应该等于aa）

在某些情况下，似乎在字符集的零位置跳过该字符。 p>

令我困惑的是，我的代码看不出什么问题。

  char * charset = （char *）abcdefghijklmnopqrstuvwxyz; 
 int charsetLength = strlen（charset）; 
 
 unsigned long long num = 5678; //一些随机数，无所谓
 std :: string key 
 
 do 
 {
 unsigned int remainder =（num％charsetLength）; 
 num / = charsetLength; 
 
 key.insert（key.begin（），charset [remainder]）; 
 
} while（num）; 
  

我有一个感觉函数是跳过模数返回零，工作这么久，我不知道它是如何发生的。欢迎任何建议。

编辑：生成的字符串是小字节序的事实与我的应用程序无关。

解决方案

如果我正确理解你想要什么（excel用于列，A，B，... Z，AA，AB，...的编号），这是一个基于符号以表示从1开始的数字.26个数字具有值1,2，... 26并且基数为26.因此A具有值1，Z值26，AA值27 ...计算此表示非常类似于正常回报，你只需要调整偏移量1而不是0。

  #include< string& 
 #include< iostream> 
 #include< climits> 
 
 std :: string base26（unsigned long v）
 {
 char const digits [] =ABCDEFGHIJKLMNOPQRSTUVWXYZ; 
 size_t const base = sizeof（digits） -  1; 
 char result [sizeof（unsigned long）* CHAR_BIT + 1]; 
 char * current = result + sizeof（result）; 
 *  -  current ='\0'; 
 
 while（v！= 0）{
 v--; 
 *  -  current = digits [v％base]; 
 v / = base; 
} 
 return current; 
} 
 
 //用于测试
 #include< cstdlib> 
 
 int main（int argc，char * argv []）
 {
 for（int i = 1; i  unsigned long value = std :: strtol（argv [i]，0，0）; 
 std :: cout<<值<< =<< base26（value）<< '\\\
'; 
} 
 return 0; 
} 
  

运行1 2 26 27 52 53 676 677 702 703给出

  1 = A 
 2 = B 
 26 = Z 
 27 = AA 
 52 = AZ 
 53 = BA 
 676 = YZ 
 677 = ZA 
 702 = ZZ 
 703 = AAA 
  pre> 
I'm trying to convert an integer to a string right now, and I'm having a problem.

I've gotten the code written and working for the most part, but it has a small flaw when carrying to the next place. It's hard to describe, so I'll give you an example. Using base 26 with a character set consisting of the lowercase alphabet:

0 = "a"

1 = "b"

2 = "c"  

...  

25 = "z"

26 = "ba" (This should equal "aa")  

It seems to skip the character at the zero place in the character set in certain situations.

The thing that's confusing me is I see nothing wrong with my code. I've been working on this for too long now, and I still can't figure it out.
char* charset = (char*)"abcdefghijklmnopqrstuvwxyz";
int charsetLength = strlen(charset);

unsigned long long num = 5678; // Some random number, it doesn't matter
std::string key

do
{
    unsigned int remainder = (num % charsetLength);
    num /= charsetLength;

    key.insert(key.begin(), charset[remainder]);

} while(num);
I have a feeling the function is tripping up over the modulo returning a zero, but I've been working on this so long, I can't figure out how it's happening. Any suggestions are welcome.

EDIT: The fact that the generated string is little endian is irrelevant for my application.
解决方案
If I understand correctly what you want (the numbering used by excel for columns, A, B, .. Z, AA, AB, ...) this is a based notation able to represent numbers starting from 1.  The 26 digits have values 1, 2, ... 26 and the base is 26. So A has value 1, Z value 26, AA value 27...  Computing this representation is very similar to the normal reprentation you just need to adjust for the offset of 1 instead of 0.
#include <string>
#include <iostream>
#include <climits>

std::string base26(unsigned long v)
{
    char const digits[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    size_t const base = sizeof(digits) - 1;
    char result[sizeof(unsigned long)*CHAR_BIT + 1];
    char* current = result + sizeof(result);
    *--current = '\0';

    while (v != 0) {
        v--;
        *--current = digits[v % base];
        v /= base;
    }
    return current;
}

// for testing
#include <cstdlib>

int main(int argc, char* argv[])
{
    for (int i = 1; i < argc; ++i) {
        unsigned long value = std::strtol(argv[i], 0, 0);
        std::cout << value << " = " << base26(value) << '\n';
    }
    return 0;
}
Running with 1 2 26 27 52 53 676 677 702 703 gives
1 = A
2 = B
26 = Z
27 = AA
52 = AZ
53 = BA
676 = YZ
677 = ZA
702 = ZZ
703 = AAA


                        
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