Thread: A question about sorting..

Hello all,
While I am preparing my test, I fould a question on a website:

How to rearrange an array of elements that either all the integers in even-numbered positions will be even or all the integers in odd-numbered positions will be odd (not necessary to establish both).

could anyone give me a simple C-like function? Thx a lot!

This is a start:

Code:

#include <stdlib.h>
#include <stdio.h>
#define ARR_SIZE 100  /* allow some extra slop */
#define WORK_SIZE 75  /* in case we have more even than odd or vice-versa */


int main(int argc, char *argv[]){        
	char *result[5]={"even","odd"};
        int odd[WORK_SIZE]={0},
            even[WORK_SIZE]={0},
            big_array[ARR_SIZE]={0};
        int i=0,
            tmp=0;
        int odd_cnt=0,
            even_cnt=0,
            big_cnt=0;
        for(i=0;i<WORK_SIZE;i++) {
                 tmp=rand();
                 if(tmp%2) 
                      odd[odd_cnt++]=tmp;
                 else
                      even[even_cnt++]=tmp;                        
        }               
        for(i=0,even_cnt=0,odd_cnt=0,big_cnt=0;odd[odd_cnt]||even[even_cnt];i++,big_cnt++){                                 
             if(big_cnt%2){
             	    if(odd[odd_cnt])
                       big_array[i]=odd[odd_cnt++];                              
             }else{
                    if(even[even_cnt])
                       big_array[i]=even[even_cnt++];                       
             }
        }
        tmp=0;
        printf("Note: a value of zero is displayed as even, but is a filler\n");
        printf("      and so can be in either an odd or an even element, regardless.\n");
        for(i=0;i<=big_cnt;i++){
              printf("element number %2d, element value %6d %-5s\n",
                        i,big_array[i],result[big_array[i]%2]);
        }
        return 0;
}

Code:

if(tmp%2)

Code:

if(big_cnt%2){

I would do this for speed and for fun

Code:

if(tmp&1==0) /*test if number is even)

and

Code:

if(big_cnt&1==0) /*test if number is even)