compare char arrays

[DERosenblum]

Hi, I'm a total newbie at programming. I am looking to compare the an
element of array2 with the next element of array2, and if equal, put a
1 in the same spot of array3.

For example, if array2[2][3] has the same value as array2[3][3], then
I want the value of array3[2][3] to be 1. My code looks like this,
thanks!!
char array2[5][10][20];
char array3[5][10];

//arrays are already populated

for(int a=0; a<5; a++)
{
for(i=0; i<10; i++)
{
if(array2[a][i] == array2[a+1][i]
{
array3[a][i]=1
}
}
}

[santosh]

DE*********@gmail.com wrote:

Hi, I'm a total newbie at programming. I am looking to compare the an
element of array2 with the next element of array2, and if equal, put a
1 in the same spot of array3.

For example, if array2[2][3] has the same value as array2[3][3],

array2[N+1][P] is _not_ the next element to array2[N][P].

then I want the value of array3[2][3] to be 1. My code looks like this,
thanks!!
char array2[5][10][20];
char array3[5][10];

//arrays are already populated

for(int a=0; a<5; a++)

C++ style comments and mixed code and declarations have been standardised
with the latest C standard, i.e., C99, which is not widely implemented. So
your code above may not compile under certain configurations.

{
for(i=0; i<10; i++)

Also symbolic constants might be better than hardcoded literals. They make
change easy and centralised.

{
if(array2[a][i] == array2[a+1][i]

Now here is a problem. When 'a' is four 'a+1' refers outside the bounds of
array2 and invokes undefined behaviour. To prevent this you need to keep
track of your loop control variables more closely.

{
array3[a][i]=1
}
}
}

[Army1987]

On Wed, 03 Oct 2007 15:45:45 -0700, DE*********@gmail.com wrote:

Hi, I'm a total newbie at programming. I am looking to compare the an
element of array2 with the next element of array2, and if equal, put a
1 in the same spot of array3.

For example, if array2[2][3] has the same value as array2[3][3], then
I want the value of array3[2][3] to be 1. My code looks like this,
thanks!!
char array2[5][10][20];
char array3[5][10];

//arrays are already populated

for(int a=0; a<5; a++)
{
for(i=0; i<10; i++)
{
if(array2[a][i] == array2[a+1][i]

Arrays evaluate to pointers to their first argument. Since
&array2[a][i][0] cannot be &array2[a+1][i][0] this is always
false. Try !memcmp(array2[a][i], array2[a+1][i], 20).

{
array3[a][i]=1
}
}
}

--
Army1987 (Replace "NOSPAM" with "email")
A hamburger is better than nothing.
Nothing is better than eternal happiness.
Therefore, a hamburger is better than eternal happiness.

[Barry Schwarz]

On Wed, 03 Oct 2007 15:45:45 -0700, "DE*********@gmail.com"
<DE*********@gmail.comwrote:

>Hi, I'm a total newbie at programming. I am looking to compare the an
element of array2 with the next element of array2, and if equal, put a
1 in the same spot of array3.

For example, if array2[2][3] has the same value as array2[3][3], then
I want the value of array3[2][3] to be 1. My code looks like this,
thanks!!
char array2[5][10][20];
char array3[5][10];

//arrays are already populated

for(int a=0; a<5; a++)
{
for(i=0; i<10; i++)
{
if(array2[a][i] == array2[a+1][i]

array2[a][i] is itself an array. In this context, the expression
evaluates to &array[a][i][0]. Similarly, the next expression
evaluates to &array2[a+1][i][0]. It should be obvious that these two
expressions can never be equal. If you are trying to determine if all
20 elements of array[a][i] are equal to the corresponding 20 elements
of array2[a+1][i], look into using memcmp.

Also note that when a is 4, you invoke undefined behavior since
array2[5][i] does not exist.

> {
array3[a][i]=1
}
}
}

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