how to merge two arrays recursevly..

**laserlight** · 01-11-2009

Originally Posted by transgalactic2

you said
else if (/* end of str2 or str1's char is less than str2's char */)

thats what i did

You need to think instead of blindly implementing a "pseudo-code" comment. If you are at the end of str1, comparing with str1's char with str2's char is wrong because there is no str1 char actually in the substring under consideration.

**~~transgalactic2~~** · 01-11-2009

i changed it to

Code:

    else if ((str2[index2]=='\0')||((str1[index1]<str2[index2])&&(str2[index2]!='\0')))

i get the same result as before

Code:

#include <stdio.h>
int merge(char str1[], int index1,char str2[],int index2, char result[], int index3);
int merge_strings(char str1[], int index1,char str2[],int index2, char result[], int index3);
int main() {
    char input[255];
    char input2[255];
    char result[510];
    int index,flag,ch;
    printf("enter the first string \n");
 for (index = 0; index < 254 && (ch = getchar()) != '\n' && ch >=0; ++index)
    {
        input[index] = ch;
    }

    input[index] = '\0';

    printf("enter the second string \n");

 for (index = 0; index < 254 && (ch = getchar()) != '\n' && ch >=0; ++index)
    {
        input2[index] = ch;
    }

    input2[index] = '\0';

    flag=merge_strings(input,0,input2,0,result, 0);

    if (flag)
    {
        printf("%s is valid.\n",result);
    }
    else
    {
        printf("%s is invalid.\n",result);
    }

return 0;
}

int merge_strings(char str1[], int index1,char str2[],int index2, char result[], int index3)
{
    if ((str1[index1] == '\0') && (str2[index2] == '\0'))
    {
        result[index3] = '\0';
        return 1;
    }
    /* non-alpha char or non-increasing order detected */
    else if ((((str1[index1]<'a')||(str1[index1]>'z'))&&((str1[index1]<'A')||(str1[index1]>'Z'))&&(str1[index1]>str1[index1+1]))&&(((str2[index2]<'a')||(str2[index2]>'z'))&&((str2[index2]<'A')||(str2[index2]>'Z'))&&(str2[index2]>str2[index2+1])))
    {
        return 0;
    }            /* end of str2 or str1's char is less than str2's char */
    else if ((str2[index2]=='\0')||((str1[index1]<str2[index2])&&(str2[index2]!='\0')))
    {
        result[index3] = str1[index1];
        return merge_strings(str1,index1+1,str2,index2,result,index3+1);
    }
    else
    {
        result[index3] = str2[index2];
        return merge_strings(str1,index1,str2,index2+1,result,index3+1);
    }
}

**laserlight** · 01-11-2009

Originally Posted by transgalactic2

i changed it to

You are supposed to check str1's char, not str2's char since you already did that in the left hand side of the expression.

**~~transgalactic2~~** · 01-11-2009

i changed it to

Code:

 else if ((str2[index2]=='\0')||((str1[index1]<str2[index2])&&(str1[index1]!='\0')))

now its just sticks those to string together(the result array is not sorted)
it says that the input is legal even if they are not legal

Code:

#include <stdio.h>
int merge(char str1[], int index1,char str2[],int index2, char result[], int index3);
int merge_strings(char str1[], int index1,char str2[],int index2, char result[], int index3);
int main() {
    char input[255];
    char input2[255];
    char result[510];
    int index,flag,ch;
    printf("enter the first string \n");
 for (index = 0; index < 254 && (ch = getchar()) != '\n' && ch >=0; ++index)
    {
        input[index] = ch;
    }

    input[index] = '\0';

    printf("enter the second string \n");

 for (index = 0; index < 254 && (ch = getchar()) != '\n' && ch >=0; ++index)
    {
        input2[index] = ch;
    }

    input2[index] = '\0';

    flag=merge_strings(input,0,input2,0,result, 0);

    if (flag)
    {
        printf("%s is valid.\n",result);
    }
    else
    {
        printf("%s is invalid.\n",result);
    }

return 0;
}

int merge_strings(char str1[], int index1,char str2[],int index2, char result[], int index3)
{
    if ((str1[index1] == '\0') && (str2[index2] == '\0'))
    {
        result[index3] = '\0';
        return 1;
    }
    /* non-alpha char or non-increasing order detected */
    else if ((((str1[index1]<'a')||(str1[index1]>'z'))&&((str1[index1]<'A')||(str1[index1]>'Z'))&&(str1[index1]>str1[index1+1]))&&(((str2[index2]<'a')||(str2[index2]>'z'))&&((str2[index2]<'A')||(str2[index2]>'Z'))&&(str2[index2]>str2[index2+1])))
    {
        return 0;
    }            /* end of str2 or str1's char is less than str2's char */
    else if ((str2[index2]=='\0')||((str1[index1]<str2[index2])&&(str1[index1]!='\0')))
    {
        result[index3] = str1[index1];
        return merge_strings(str1,index1+1,str2,index2,result,index3+1);
    }
    else
    {
        result[index3] = str2[index2];
        return merge_strings(str1,index1,str2,index2+1,result,index3+1);
    }
}

**laserlight** · 01-11-2009

Originally Posted by transgalactic2

now its just sticks those to string together(the result array is not sorted)
it says that the input is legal even if they are not legal

What test input did you use?

**itCbitC** · 01-11-2009

Originally Posted by transgalactic2

now its just sticks those to string together(the result array is not sorted)
it says that the input is legal even if they are not legal

what do you mean by the above? can you provide an example of the output you're getting.

**~~transgalactic2~~** · 01-11-2009

this is a print screen of the input

http://img258.imageshack.us/img258/6168/46740647tq4.gif

Code:

#include <stdio.h>
int merge(char str1[], int index1,char str2[],int index2, char result[], int index3);
int merge_strings(char str1[], int index1,char str2[],int index2, char result[], int index3);
int main() {
    char input[255];
    char input2[255];
    char result[510];
    int index,flag,ch;
    printf("enter the first string \n");
 for (index = 0; index < 254 && (ch = getchar()) != '\n' && ch >=0; ++index)
    {
        input[index] = ch;
    }

    input[index] = '\0';

    printf("enter the second string \n");

 for (index = 0; index < 254 && (ch = getchar()) != '\n' && ch >=0; ++index)
    {
        input2[index] = ch;
    }

    input2[index] = '\0';

    flag=merge_strings(input,0,input2,0,result, 0);

    if (flag)
    {
        printf("%s is valid.\n",result);
    }
    else
    {
        printf("%s is invalid.\n",result);
    }

return 0;
}

int merge_strings(char str1[], int index1,char str2[],int index2, char result[], int index3)
{
    if ((str1[index1] == '\0') && (str2[index2] == '\0'))
    {
        result[index3] = '\0';
        return 1;
    }
    /* non-alpha char or non-increasing order detected */
    else if ((((str1[index1]<'a')||(str1[index1]>'z'))&&((str1[index1]<'A')||(str1[index1]>'Z'))&&(str1[index1]>str1[index1+1]))&&(((str2[index2]<'a')||(str2[index2]>'z'))&&((str2[index2]<'A')||(str2[index2]>'Z'))&&(str2[index2]>str2[index2+1])))
    {
        return 0;
    }            /* end of str2 or str1's char is less than str2's char */
    else if ((str2[index2]=='\0')||((str1[index1]<str2[index2])&&(str1[index1]!='\0')))
    {
        result[index3] = str1[index1];
        return merge_strings(str1,index1+1,str2,index2,result,index3+1);
    }
    else
    {
        result[index3] = str2[index2];
        return merge_strings(str1,index1,str2,index2+1,result,index3+1);
    }
}

**laserlight** · 01-11-2009

That implies that your "non-alpha char or non-increasing order detected" code is incorrect. Now is a good time to practice your debugging skills.

**itCbitC** · 01-11-2009

Whoops! forgot to ask you how the output should look like because I can barely make out the image you posted.

**laserlight** · 01-11-2009

Originally Posted by itCbitC

Whoops, forgot to ask you how the output should look like because I can barely make out the image you posted.

The inputs were "gabc" and "gsfg" and the main output was "dgabcsfg" instead of an invalid input message.

Basically, transgalactic2 forgot to check for null characters (again).

**itCbitC** · 01-11-2009

Originally Posted by laserlight

The inputs were "gabc" and "gsfg" and the main output was "dgabcsfg" instead of an invalid input message.

Basically, transgalactic2 forgot to check for null characters (again).

Ah! well that would explain why.

**~~transgalactic2~~** · 01-11-2009

i noticed that it skips this line
although it should go inside of it

Code:

 else if ((((str1[index1]<'a')||(str1[index1]>'z'))&&((str1[index1]<'A')||(str1[index1]>'Z'))&&(str1[index1]>str1[index1+1]))&&(((str2[index2]<'a')||(str2[index2]>'z'))&&((str2[index2]<'A')||(str2[index2]>'Z'))&&(str2[index2]>str2[index2+1])))
    {

i cant see the problem in it
??

**~~transgalactic2~~** · 01-11-2009

what null characters?

i specifically told the not legal ascii ranges
where is my mistake
regarding the null thing?

**laserlight** · 01-11-2009

Originally Posted by transgalactic2

what null characters?

As in '\0', the terminating null character for a string. This is basically a variant of the problem that you solved just a while ago by adding the str1[index1]!='\0' expression.

**itCbitC** · 01-11-2009

I know I'm jumping into this thread late, but it would help if you indented the code so it doesn't scroll off the page making it exceedingly hard to read and understand.