c - 尝试重建 itoa 功能

Question

我的程序仅输出非零数字...例如输入= 16076，输出= 1676 ...任何人都可以帮忙数学

#include <stdio.h>

char        *ft_itoa(int n)
{

    int count;
    int i;
    int j = 0;
    int temp;
    int allocated = 0;
    char *val;
    int zero;
    while (n > 0)
    {
        count = n;
        i = 0;
        temp = 1;

        while (count > 0)
        {
            i++;
            count /= 10;
            printf("works %d\n", i);
        }
        if (allocated == 0)
        {
            printf("alocated\n");
            allocated = 1;
            val = (char *)malloc((i + 1) * sizeof(char));
        }

        while (i > 1)
        {
            temp *= 10;
            i--;
            //printf("temp = %d\n", temp);
        }
        val[j] =  n / (temp) + '0';
        n = n - ((temp) * (n / temp));
        //val++;

Answer 1

您的代码中存在几个问题，与您没有模仿通常的atoi(它在参数中获取字符串，更多的基础，并且也适用于负数)这一事实无关 p>

• 您没有更改j的值，因此您只修改了val[0]，并且由于循环的结尾不可见，我们不可见知道您是否将最后一个空字符放在某处

• 你的代码很复杂，比如为什么每轮都要计算位数和十的幂？

• 显然你不知道模运算符“%”存在

• 零没用

my program on only outputs none zero numbers

这是因为你计算每轮位数的方式，在你从 16076 中删除两个较高的数字后，你得到 076，所以实际上是 76 并且你绕过了 0

计算一次位数后，正确的方法是从较低的数字开始以相反的顺序写入数字

例如，如果像您一样我分配字符串并且仅管理正数，则解决方案可以是:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char ** argv)
{
  if (argc != 2)
    printf("Usage: %s <positive number>\n", *argv);
  else {
    int n;

    if ((sscanf(argv[1], "%d", &n) != 1)  || (n < 0))
      fprintf(stderr, "invalid number '%s'\n", argv[1]);
    else {
      int v;
      size_t ndigits;

      if (n == 0)
        ndigits = 1;
      else 
        for (v = n, ndigits = 0; v != 0; v /= 10, ++ndigits)
          ; /* empty body */

      char * s = malloc(ndigits + 1);

      s[ndigits] = 0;

      do {
        s[--ndigits] = n % 10 + '0';
        n /= 10;
      } while (ndigits != 0);

      puts(s);
      free(s);
    }
  }

  return 0;
}

编译和执行:

pi@raspberrypi:/tmp $ gcc -g -pedantic -Wextra -Wall i.c
pi@raspberrypi:/tmp $ ./a.out 16076
16076
pi@raspberrypi:/tmp $ 

在valgrind下执行:

pi@raspberrypi:/tmp $ valgrind ./a.out 16076
==6822== Memcheck, a memory error detector
==6822== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==6822== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==6822== Command: ./a.out 16076
==6822== 
16076
==6822== 
==6822== HEAP SUMMARY:
==6822==     in use at exit: 0 bytes in 0 blocks
==6822==   total heap usage: 2 allocs, 2 frees, 1,030 bytes allocated
==6822== 
==6822== All heap blocks were freed -- no leaks are possible
==6822== 
==6822== For counts of detected and suppressed errors, rerun with: -v
==6822== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 3)
pi@raspberrypi:/tmp $