Thread: sorting a 2d array by column

Hey i have a matrix containing a lot of points and each point has its coordinates x and y. That is a nx2 size array. I want to sort it according to the first column ascending, with x coordinates. For points that have the same x coord i would like to sort according to y coord. Here is what i did and i cannot get a good result.

Code:

#include <stdio.h>                                 
#include <stdlib.h>                                
int main(){
int a[5][2] = {{1,0}, {4,2}, {2,4}, {8,6},{4,8}};
int temp=0;
int i=0;
int j=0;

for(int y=0; y<2; y++)
    {
	for(int x=0; x<5;x++)	
		{
	
        if(a[x][y] < a[0][y])
            {
                temp=a[x][y];
                a[0][0]=a[x][y];
                a[0][0]=temp;
            
            }
        }
    }

   for ( i = 0; i < 5; i++ )
   {
      for ( j = 0; j < 2; j++ )
      {
         printf("a[%d][%d] = %d\n", i,j, a[i][j] );
      }
   }
return 0;}

Have you looked at sorting before at all? Do you have an algorithm in mind for how you want to sort?

You can put it all in 1D array then sort and put it in the matrix again as you want it.

ok done it here it is

Code:

	for(int xcord=0;xcord<5;xcord++){
		for(int ycord=xcord+1;ycord<5;ycord++){
			if(a[xcord][0]>a[ycord][0]){
			
				int temp = a[xcord][1];
				int temp2=a[xcord][0];
				a[xcord][0]=a[ycord][0];
				a[xcord][1]=a[ycord][1];
				a[ycord][0]=temp2;
				a[ycord][1]=temp;
				}
		}
	}