3/4.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55

#include <limits.h>
#include <stdio.h>
#include <string.h>

#define MAXLEN 50

void itoa(int n, char s[]);
void reverse(char s[]);

/* fixes itoa function to handle the largest negative number */
int main(int argc, char *argv[]) {
  char s[MAXLEN];

  itoa(INT_MIN, s);
  printf("Largest negative number on machine: %d\n", INT_MIN);
  printf("Largest negative number after itoa: %s\n", s);

  return 0;
}

void itoa(int n, char s[]) {
  int i, sign;

  i = 0;
  sign = n < 0;

  if (!sign) {
    do {
      s[i++] = n % 10 + '0';
    } while ((n /= 10) > 0);
  }
  else {
    // avoid integer overflow of n = -n for min integer in original impl
    // by handling negtive values separately.
    do {
      s[i++] = -(n % 10) + '0';
    } while ((n /= 10) <= -1);
  }

  if (sign)
    s[i++] = '-';
  s[i] = 0;
  
  reverse(s);
}

void reverse(char s[]) {
  int c, i, j;

  for (i = 0, j = strlen(s) - 1; i < j; i++, j--) {
    c = s[i];
    s[i] = s[j];
    s[j] = c;
  }
}