Loop output of indeterminate length data without spaces at the end

Question requirements: Input two positive integers a and b, find the prime numbers between [a, b], and output from small to large.

                (2 <= a <= b <=1000000)，

Output the prime numbers between [a,b], separate the prime numbers with a space, and each output occupies one line.

It is equivalent to outputting data of indeterminate length, the prime numbers are separated by spaces, and there is no space at the end.

I don't know what method you used when you first encountered this problem.

What I thought of is: the first input without spaces, directly printed in the form of %d, and only output in this form once.

Every time after that is printed as space + %d so that there is no space at the end of the output.

Code directly below:

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

 int main()
{	
	 int m, n;
	 while (~scanf("%d %d", &m, &n))
	 {	
		 int k = 1;
		 for (m; m <= n; m++)
		 {	
			 int b = (int)sqrt(m);
			 int flag = 1;
			 for (int a = 2; a <= b; a++)
			 {
				 if ((m % a) == 0)
				 {
					 flag = 0;
					 break;
				 }
			 }
			 if (flag == 1)
			 {
				 if (k == 1)
				 {
					 printf("%d", m);//只输入一次
					 k = 0;
				 }
				 else
					 printf(" %d", m);
			 }
				
			 }
		 printf("\n");
		 getchar();
	}

	 return 0;
 }

This way there are no spaces at the end.

I hope this article is helpful to you, if you have any questions, please feel free to correct me.