7.5 ARRAYS AND STRINGS

Most C compilers include library functions that allow strings to be compared, copied or concatenated (i.e combined, one behind another).Other library functions permit operations on individual characters within strings; e.g., they allow individual characters to be located within strings, and so on.The following example illustrates the use of some of these library functions.

/* sort a list of strings alphabetically using a two-dimensional character array*/

#include < stdio.h >

#include < stdlib.h >

#include < string.h >

void reorder (int n, char x[][12]);  /* function prototype*/

main()

{

int i, n = 0;

char x[10][12];

printf ("Enter each string on a separate line below\n\n");

printf ("Type \ 'END\ ' when finished\n\n");

/*read in the list of strings*/

do  {

printf ("string %d: ", n+1);

scanf ("%s", x[n]);

} while (strcmp(x[n++], "END"));

/* adjust the value of n*/

n--;

/* reorder the list of strings*/

reorder(n, x);

/* display the reordered list of strings */

printf("\n\nReordered List of strings: \n");

for (i=0; i < n;++i)

printf("\nstring %d: %s", i+1, x[i]);

}

void reorder(int n, char x[][12])  /* rearrange the list of strings */

{

char temp[12];

int i, item ;

for (item=0; item <  n-1;++item)

/* find the lowest of all remaining strings */

for (i=item+1; i <  n;++i)

if (strcmp(x[item], x[i]) > 0)  {

/* interchange the two strings */

strcpy(temp, x[item]);

strcpy(x[item], x[i]);

strcpy(x[i], temp);

}

return;

}

The strcmp function appears in two different places within this program : in main, when testing for a stopping condition, and in rearrange, when testing for the need to interchange two strings.The actual string interchange is carried out using strcpy.The dialog resulting from a typical execution of the program is shown below.The user's response are underlined, as usual.

Enter each string on a separate line below

Type 'END ' when finished

string 1: PACIFIC

string 2: ATLANTIC

string 3: INDIAN

string 4: CARIBBEAN

string 5: BERING

string 6: BLACK

string 7: RED

string 8: NORTH

string 9: BALTIC

string 10: CASPIAN

string 11: END

Reordered List of strings:

string 1: ATLANTIC

string 2: BALTIC

string 3: BERING

string 4: BLACK

string 5: CARIBBEAN

string 6: CASPIAN

string 7: INDIAN

string 8: NORTH

string 9: PACIFIC

string 10: RED