How do you sort names alphabetically using pointers?

Answer 1

#include
#include

int main(void)
{
int item[100];
int a, b, t;
int count;
printf("How many numbers? ");
scanf("%d", &count);

for(a = 0; a < count; a++)
scanf("%d", &item[a]);

for(a = 1; a < count; ++a)
for(b = count-1; b >= a; --b) {
if(item[ b - 1] > item[ b ]) {
t = item[ b - 1];
item[ b - 1] = item[ b ];
item[ b ] = t;
}
}

for(t=0; t

return 0;
}

Answer 2

#include <stdlib.h>

int int_sorter( const void *first_arg, const void *second_arg )

{

int first = *(int*)first_arg;

int second = *(int*)second_arg;

if ( first < second )

{

return -1;

}

else if ( first == second )

{

return 0;

}

else

{

return 1;

}

}

int main()

{

int array[10];

int i;

/* fill array */

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

{

array[ i ] = 10 - i;

}

qsort( array, 10 , sizeof( int ), int_sorter );

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

{

printf ( "%d\n" ,array[ i ] );

}

Answer 3

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

void print2d(char **, size_t);

void selectionSort2d(char **, size_t);

char *names[] = {"John", "Joe", "Genevieve", "Mark", "Luke", "Jane" };

int main(int argc, char *argv[]) {

char **strArray;

size_t i, len = sizeof(names) / sizeof(char *);

/* Allocate */

strArray = calloc(len,sizeof(char*));

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

strArray[i] = calloc(strlen(names[i]),sizeof(char));

strcpy(strArray[i],names[i]);

}

/* Display */

printf("\nUnsorted:\n");

print2d(strArray,len);

/* Sort */

selectionSort2d(strArray,len);

/* Display */

printf("\nSorted:\n");

print2d(strArray,len);

/* Free */

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

free(strArray[i]);

}

return 0;

}

void selectionSort2d(char **a, size_t rows) {

int i, j, min;

char *t;

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

min = i;

for (j = i+1; j < rows; j++) {

if (strcmp(a[j],a[min]) < 0) {

min = j;

}

}

t = a[min];

a[min] = a[i];

a[i] = t;

}

}

void print2d(char **a, size_t rows) {

size_t i;

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

printf("%s\n",a[i]);

}

}

Answer 4

You simply need to create an array of char pointers. Assign to each element the memory address of an unique string. Then sort the array of pointers.

The following example demonstrates how to sort literal strings using a static pointer array. The code can be adapted to cater for dynamically allocated strings as well as a dynamic array of pointers (allocated via a pointer-to-pointer).

#include <iostream>

int main()

{

const int max = 4;

// Instantiate an array of pointers to literal strings.

// Note that the literal strings are not stored in the

// array. Since the strings are literal, they are

// each allocated 16 bytes within the program's data

// segment. The array is also allocated in the data

// segment, but the elements contain pointers to

// the strings, not the string themselves.

char * names[max] = { "Hartley, John", "Evans, Steven", "Forbes, David", "Burns, Paul" };

// The size of the array is 16 bytes, not 64 bytes,

// because it only contains 4 pointers, not 4 strings.

printf( "Size of array: %u bytes\n\n", sizeof( names ));

// Print the unsorted array: the element address, the

// value stored in that element (a memory address) and

// the value stored at that address (the string itself).

printf( "Unsorted\n");

for( int i=0; i<max; ++i )

printf( "0x%.8x : 0x%.8x : %s\n", &names[i], names[i], names[i] );

printf( "\n" );

// Insertion sort.

for( int i=1; i<max; ++i )

{

char * item = names[i];

int iHole = i;

while( iHole > 0 && strcmp( names[iHole-1], item ) > 0 )

{

names[iHole] = names[iHole-1];

iHole=iHole-1;

}

names[iHole]=item;

}

// Print the sorted array: the element address, the

// value stored in that element (a memory address) and

// the value stored at that address (the string itself).

printf( "Sorted\n" );

for( int i=0; i<max; ++i )

printf( "0x%.8x : 0x%.8x : %s\n", &names[i], names[i], names[i] );

printf( "\n" );

// Note that each string still resides in the same memory address.

// They have not moved! Only the pointers to those strings have

// actually been sorted.

return(0);

}