sorting function and while loop.

Hello,

I am having trouble with my sorting function. I am trying to sort 5 strings. After I input all 5 strings, the program hangs. When I comment out the while loop, it prints the five strings(though not sorted), so the problem is with the while loop. I can't seem to find what I am doing wrong. Any suggestions?

Code:

void string_sort(char * strings[], int num)
{
	char *temp;
	int i, j;
	int sorted = 0;
	
	while(sorted!=1)
	{
		sorted = 1;
		for(i=0; i<num-1; i++)
			for(j=1; j<num; j++)
				{
				if(strcmp(strings[i], strings[j]) > 0)
					{
					temp = strings[i];
					strings[i] = strings[j];
					strings[j] = temp;
					sorted = 0;
					}
				}
	}
}

use strcpy() for copying strings.

Originally Posted by swappo

Hello,

I am having trouble with my sorting function. I am trying to sort 5 strings. After I input all 5 strings, the program hangs. When I comment out the while loop, it prints the five strings(though not sorted), so the problem is with the while loop. I can't seem to find what I am doing wrong. Any suggestions?

Code:

void string_sort(char * strings[], int num)
{
	char *temp;
	int i, j;
	int sorted = 0;
	
	while(sorted!=1)
	{
		sorted = 1;
		for(i=0; i<num-1; i++) {
			for(j=1; j<num; j++)
				{
				if(strcmp(strings[i], strings[j]) > 0)
					{
					temp = strings[i];
					strings[i] = strings[j];
					strings[j] = temp;
					sorted = 0;
					}
				}
               }
	}
}

The outermost for loop is mssing its opening / closing parenthesis.
Is strings[] a 5-numbered array of pointers to strings.

The while loop doesn't make any sense to me.
edit:
@itcbitc
I think that's not an error but good practice though to use the brackets.

The purpose of the while loop is to keep looping through the for loops until the list is completely sorted. With out the while loop, I would expect the program to terminate after going through the for loops leaving the array of strings partially sorted. When I comment out the while loop, I get partially sorted strings.

I couldn't understand how the while loop is being used in this context.
Could you post your complete code please?

Could you post the code that fills in the strings and calls the sort function? I suspect stevesmithx is on the right track, but it's hard to say without knowing exactly what the strings look like and how they are stored.

--
Mats

The string_sort function looks okay to me, actually. I suggest that you post the smallest and simplest compilable code that demonstrates the problem.

Here is the whole program.

Code:

#include <stdio.h>
#include <string.h>
#include <math.h>

void string_sort(char * strings[], int num);

int main(void)
{
	char input[5][100]={'\0'};
	char ch;
	char * ptstr[5];
	int i, j, k;
	
	printf("Enter 5 strings\n");
	for(i=0; i<5; i++)
		for(j=0; (ch=getchar())!='\n'; j++)
			{
			input[i][j]=ch;
			ptstr[i]=input[i];
			}
	printf("\n");
	string_sort(ptstr, i);

	for(i=0; i<5; i++)
		{
		for(j=0; j<100; j++)
			printf("%c", ptstr[i][j]);
		printf("\n");
		}
	return 0;
}
void string_sort(char * strings[], int num)
{
	char *temp;
	int i, j;
	int sorted = 0;
	
	while(sorted!=1)
	{
		sorted = 1;
		for(i=0; i<num-1; i++)
			{
			for(j=1; j<num; j++)
				{
				if(strcmp(strings[i], strings[j]) > 0)
					{
					temp = strings[i];
					strings[i] = strings[j];
					strings[j] = temp;
					sorted = 0;
					}
				}
			}
	}
}

use strcpy() instead of assigning strings.
[Didn't you read my first post]

Considering that you do not even pass a char *string[] to the code, I'd say you're very lucky to not crash...

You need to pass your strings as a 2D array of char, string[][100], and use strcpy() to move the content around.

--
Mats

Originally Posted by matsp

You need to pass your strings as a 2D array of char, string[][100], and use strcpy() to move the content around.

Alternatively, you can actually have an array of pointers to char, e.g., with dynamic memory allocation for each string. The crux of the problem is that your function is designed to work with an array (or rather a pointer to the first element of an array) of pointers, but what you have is a two dimensional array.

[QUOTEuse strcpy() instead of assigning strings.
[Didn't you read my first post] ][/QUOTE]
Yes I did read your post and I was planning on trying strcpy() next. First, I wanted to see if I can get it to work the way it is so far.

Originally Posted by swappo

[QUOTEuse strcpy() instead of assigning strings.
[Didn't you read my first post] ]

Yes I did read your post and I was planning on trying strcpy() next. First, I wanted to see if I can get it to work the way it is so far.[/QUOTE]

No, you can't because what you are doing to the variable when you are passing it to the function is wrong.

You can prove that by printing the strings inside the sort function.

--
Mats

I agree with mats and laserlight.
You can keep it simple if you use two dimensional arrays throughout.
Also you can use functions like scanf/fgets to get the string from stdin more easily.