c loop stops when array value is zero not null - c

Question

int findMax(int*sums){
int t = 0;
int max = sums[0];
while (sums[t] != '\0'){
printf("current max: %d %d\n", max, sums[t]);
if (sums[t] > max ){
max = sums[t];
}
t ++;
}
return max;
}
This outputs:
current max: 7 7
current max: 7 4
current max: 7 2
And its ignoring the rest of the list, sums. I think this is because the next element in sums is 0. But I can't see why it would treat 0 as '\0' (null).

Answer 1

sums is an array of integers (technically a pointer to integer). '\0' (the null byte) and 0 are the same value, so your loop will stop when it encounters a 0. There is no such thing as a null value as far as integers are concerned. The term "null" is used to refer to the value NULL, which is a pointer usually with the value 0 (i.e., a pointer that doesn't point to anything), and also the null (0) byte, such as the one that occurs at the end of a null-terminated string.

Answer 2

I do remember the time when I first encountered the same problem ( while I was trying to build a big number library using int arrays ), and eventually I figured out pretty much the same as what other answers say that technically '\0' and 0 have the same value.
Now here are 2 ways that I used to overcome this problem and these are only applicable under certain conditions
Case 1 :
Condition : When all your input elements are positive
Now since all your input elements are positive, you can mark the end of the array by inserting a negative number
Typically, I use -1, this way :
int a[] = {1, 2, 3, 4, -1}
for(int index = 0; a[index] != -1; index++)
{
//use the array element a[index] for desired purpose!
}
Instead you can enter any negative number and do it this way
for(int index = 0; a[index] >= 0; index++)
{
//use the array element a[index] for desired purpose!
}
Case 2 :
Condition : When all your elements are bound within a certain range
You might have got the idea by now :), lets say that all your elements belong to the range [-100,100]
you can insert any number above or below the bounds of the range to mark the end... so in the above case I can mark the end by entering a number < -100 and >100.
And you can iterate the loop this way :
for(int index = 0; (a[index] > -100) && (a[index] < 100); index++)
{
//use the array element a[index] for desired purpose!
}
Generalizing both the cases, just place a value at the end of array which you know for sure is not equal to an array element
for(int index = 0; a[index] != value_not_in_array; index++)
{
//use the array element a[index] for desired purpose!
}
So, now under Case 1, your while loop condition can be either of the following :
while(sums[t] != -1) //typically ended with `-1`
//(or)
while (sums[t] >= 0) //ended with any negative number
And under Case 2 :
while ((sums[t] >min_range) && (sums[t] < max_range)) // when elements are bound within a range
Or more generally :
while( sums[t] != value_not_in_array )
The underlying fact of both the cases is that I'm finding out a
potential replacement for terminating '\0' character.
Hope this helps, happy coding ;)

Answer 3

'\0' is a representation of a non-printable ASCII character. Specifically, it is the character 0 (as in, the zeroeth character, not the character '0', whichis 48. Look it up on an ASCII table).
'\0' is the same as 0 the same way 'A' is == 65. There is no difference as far as the compiler is concerned. '\0' == 0 will always evaluate as true.
Note that only strings are terminated with a '\0', unlike all other arrays.

Answer 4

In C, the character literal '\0' has the value (int)0, that's what the escape sequence translates to.
#include <stdio.h>
int main() {
int i = 0;
char c = '\0';
printf("%s\n", (i == c) ? "same" : "different");
}
http://ideone.com/sYRbYZ

Answer 5

I think you're confusing a pointer check for NULL vs a value check for zero.
Here are two slightly different variants of your function to illustrate the point:
#include <stdio.h>
int
findPtr(int **sums)
{
int t = 0;
int max = *sums[0];
int val;
while (sums[t] != NULL) {
val = *sums[t];
printf("current max: %d %d\n", max, val);
if (val > max) {
max = val;
}
t++;
}
return max;
}
int
findArr(int *sums,int count)
{
int t = 0;
int max = sums[0];
while (t < count) {
printf("current max: %d %d\n", max, sums[t]);
if (sums[t] > max) {
max = sums[t];
}
t++;
}
return max;
}
Since zero (either 0 or \0--which are equivalent) is a valid value in sums, it can't be used as a sentinel for end of array as your check was doing. You'll need to pass down the array count as in the latter example.

Answer 6

In your code, you are taking a pointer to an array of integers as input in the findMax function. '\0' is a character. You are comparing integers to a character, causing the compiler to cast the character '\0' and use its integer equivalent NULL (or simply 0). Therefore the program stops when it comes to a 0 in the array.
You might want to try :
int findMax(int*sums,int arraysize)
{
int t=0;
int max = sums[t];
while(t<arraysize)
{
printf("current max: %d %d\n", max, sums[t]);
if (sums[t] > max )
{max = sums[t];}
t++;
}
return max;
}