[英]Converting base 20 to int
I am trying to convert base 20 to int
. 我试图将基数20转换为int
。 For example if I have "1A"
it needs to be converted to 30
, and so on. 例如,如果我有"1A"
则需要将其转换为30
,依此类推。 I have developed the code but it is giving issues in running. 我已经开发了代码,但是在运行中却出现了问题。 Code is as below in C programming language: 代码如下使用C编程语言:
#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("Hello world!\n");
char converted[20] = "1A";
itov(converted);
return 0;
}
void itov(char vigesimalStr[])
{
int length = 0;
for (int i = 0; vigesimalStr[i] != '\0'; i++)
{
length++;
}
int base = 20;
int result = 0;
int power = 1;
int num = 0;
for (int j = length; j >= 0; j--)
{
if (val(vigesimalStr[j]) >= base)
{
printf("Invalid Number");
return -1;
}
num += val(vigesimalStr[j]) * power;
power = power * base;
}
}
int val(char c)
{
if (c >= '0' && c <= '9')
return (int)c - '0';
else
return (int)c - 'A' + 10;
}
I will begin by stating the obvious, there is already a library function that can convert a string containing a number in any base from (I believe) 2 to 36: 首先,我要说明一个明显的问题,已经有一个库函数可以将包含任何基数的字符串从(我相信)2转换为36:
printf("%ld\n", strtol("1A", NULL, 20));
// Output: 30
If, however, as part of an exercise or homework assignment the use of this and similar library functions are prohibited, I will not do your homework for you, but I will instead give you a description of the high level algorithm for reading an integer in an arbitrary base, N: 但是,如果作为练习或家庭作业的一部分,禁止使用此函数和类似的库函数,则我不会为您做家庭作业,而是向您介绍在其中读取整数的高级算法。任意基数N:
accumulator
variable at zero. 将accumulator
变量初始化为零。 i
at 0
. 将计数变量i
初始化为0
。 accumulator
by N. 将accumulator
乘以N。 str[i]
, and add that to accumulator
(your val
function). 获取str[i]
当前以N为底的数字的数值,并将其添加到accumulator
(您的val
函数)。 i
. 递增i
。 str[i]
is '\\0'
, return accumulator
and exit. 如果str[i]
为'\\0'
,则返回accumulator
并退出。 Otherwise, go to step 3. 否则,请转到步骤3。 Two key issues I see in your code: 我在您的代码中看到了两个关键问题:
void itov(char vigesimalStr[])
// ...
return -1;
The itov()
function can't be void
if it returns -1 on error. 如果错误返回-1,则itov()
函数不能为void
。 It also fails to return the correct value on success! 成功也不会返回正确的值!
for (int j = length; j >= 0; j--)
When running a sequence backward, you want to start at length - 1
as length
itself is never a valid index as it's the last index plus one. 向后运行序列时,您要从length - 1
开始length - 1
因为length
本身永远不是有效的索引,因为它是最后一个索引加一个。
Below is a rework of your code with the above issues fixed and other lesser issues tidied up: 下面是对代码的重做,修复了上述问题,并整理了其他一些较小的问题:
#include <stdio.h>
#include <stdlib.h>
#define BASE 20
int val(char c)
{
if ('0' <= c && c <= '9')
return c - '0';
return c - 'A' + 10;
}
int itov(char vigesimalStr[])
{
int length = 0;
for (length = 0; vigesimalStr[length] != '\0'; length++)
{
// nothing to see here
}
int power = 1;
int number = 0;
for (int j = length - 1; j >= 0; j--)
{
int digit = val(vigesimalStr[j]);
if (digit >= BASE)
{
fprintf(stderr, "Invalid Number\n");
return -1;
}
number += digit * power;
power *= BASE;
}
return number;
}
int main()
{
char to_convert[20] = "1A";
printf("%d\n", itov(to_convert));
return 0;
}
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