在数组中交换奇数和偶数，C

Question

Input array is for example Array[10] = {12,23,0,-7,138,22,7,99,10,-2}

I want to print out the array with even numbers on one end and odd numbers on the other, something like this: Array[10] = {12,0,-2,10,22,138,-7,99,7,23}

int main()
{
    int N = 0, i = 0, j = N-1, index = 0;
    printf("Enter N (0>N<10): ");
    scanf("%d", &N);

    int Array[N];
    for(i=0;i<N;i++){
        printf("Enter the value number %d :", i+1);
        scanf("%d", &Array[i]);
    }
    printf("Array[%d] ={",N);
    for(i=0;i<N;i++){
        printf("%d\t", Array[i]);
    }
    printf("}");

    // swaping odd and even numbers

    int Array2[N];
    while (i < j){
        if(Array[i]%2 == 0){
            Array2[i] = Array[index];
            i++;
        }
        else{
            Array2[j] = Array[index];
            j++;
        }
        index++;
    }

    // view the new array

    printf("\n Array[%d] ={",N);
    for(i=0;i<N;i++){
        printf("%d\t", Array2[i]);
    }
    printf("}");

    return 0;
}

This doesn't seem to work. Any help would be appreciated.

Note: I know the Array[N] part is not how it's supposed to be done, it's just to simplify things.

Answer 1

Here's an idea I just came up with. I haven't tested it, that's up to you (this is just pseudo-code).

array[n] = {...}
newarray[n]
i = 0
j = n-1
index = 0
while (i < j){
    if (array[index] is even)
        newarray[i] = array[index]
        i = i + 1
    else
        newarray[j] = array[index]
        j = j -1
    index = index + 1
}

Answer 2

This is analogous to the Partition section of Quicksort, except instead of dividing elements by comparing them to a pivot, you use their even/odd-ness. One benefit is not needing a second "scratch" array. (Your example did not seem to care about the order of either side, just the proper partitioning.)

int i = 0;
int j = n-1;
while ( i < j ) {
    // Invariant: Array[0..i-1] are even and Array[j+1..n-1] are odd
    while ( Array[i] % 2 == 0 ) // Array[0..i] is even
        i++;
    while ( Array[j] % 2 == 1 ) // Array[j..n-1] is odd
        j--;
    if ( i < j ) { // Array[j] and Array[i] are in the wrong sides
        // Swap them into the correct sides
        int temp = Array[i];
        Array[i] = Array[j];
        Array[j] = temp;
        // Now we can extend each correct side
        i++;
        j--;
    }
}