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  1. #include <stdio.h>
  2.  
  3. double myStrtod(const char *string)
  4. {
  5.     double number = 0.0;
  6.     double decimalPlace = 0.1;
  7.     int sign = 1;
  8.     int i = 0;
  9.  
  10.     while (string[i] == ' ')
  11.     {
  12.         ++i;
  13.     }
  14.  
  15.     if (string[i] == '-')
  16.     {
  17.         sign = -1;
  18.         ++i;
  19.     }
  20.     else if (string[i] == '+')
  21.     {
  22.         ++i;
  23.     }
  24.  
  25.     while (string[i] >= '0' &&
  26.            string[i] <= '9')
  27.     {
  28.         number = number * 10 +
  29.                  (string[i] - '0');
  30.  
  31.         ++i;
  32.     }
  33.  
  34.     if (string[i] == '.')
  35.     {
  36.         ++i;
  37.  
  38.         while (string[i] >= '0' &&
  39.                string[i] <= '9')
  40.         {
  41.             number +=
  42.                 (string[i] - '0') * decimalPlace;
  43.  
  44.             decimalPlace *= 0.1;
  45.             ++i;
  46.         }
  47.     }
  48.  
  49.     return sign * number;
  50. }
  51.  
  52. long myStrtol(const char *string)
  53. {
  54.     long number = 0;
  55.     int sign = 1;
  56.     int i = 0;
  57.  
  58.     while (string[i] == ' ')
  59.     {
  60.         ++i;
  61.     }
  62.  
  63.     if (string[i] == '-')
  64.     {
  65.         sign = -1;
  66.         ++i;
  67.     }
  68.     else if (string[i] == '+')
  69.     {
  70.         ++i;
  71.     }
  72.  
  73.     while (string[i] >= '0' &&
  74.            string[i] <= '9')
  75.     {
  76.         number = number * 10 +
  77.                  (string[i] - '0');
  78.  
  79.         ++i;
  80.     }
  81.  
  82.     return sign * number;
  83. }
  84.  
  85. unsigned long myStrtoul(const char *string)
  86. {
  87.     unsigned long number = 0;
  88.     int i = 0;
  89.  
  90.     while (string[i] == ' ')
  91.     {
  92.         ++i;
  93.     }
  94.  
  95.     while (string[i] >= '0' &&
  96.            string[i] <= '9')
  97.     {
  98.         number = number * 10 +
  99.                  (string[i] - '0');
  100.  
  101.         ++i;
  102.     }
  103.  
  104.     return number;
  105. }
  106.  
  107. int main(void)
  108. {
  109.     char doubleString[] = "-123.456";
  110.     char longString[] = "-1234567";
  111.     char unsignedString[] = "1234567";
  112.  
  113.     printf("Double value = %.3f\n",
  114.            myStrtod(doubleString));
  115.  
  116.     printf("Long value = %ld\n",
  117.            myStrtol(longString));
  118.  
  119.     printf("Unsigned long value = %lu\n",
  120.            myStrtoul(unsignedString));
  121.  
  122.     return 0;
  123. }
Success #stdin #stdout 0s 5356KB
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stdin
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Standard input is empty
stdout
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Double value = -123.456
Long value = -1234567
Unsigned long value = 1234567
https://ideone.com/xHPAfu
language:
C (gcc 8.3)
created:
3 hours ago
visibility:
public

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