Mergesort

Mergesort.java

public void sort( int[] numbers ){
    mergesort( numbers );
}

public void mergesort( int[] numbers ){
    if( numbers.length > 1 ){
        int[] leftHalf  = splitLeft( numbers );
        int[] rightHalf = splitRight( numbers );
        mergesort( leftHalf );
        mergesort( rightHalf );
        merge( numbers, leftHalf, rightHalf );
    }
}

public int[] splitLeft( int[] numbers ){
    int[] left = new int[numbers.length/2];
    for ( int i = 0; i < numbers.length/2; i++ ){
        left[i] = numbers[i];
    }
    return left[i];
}

public int[] splitRight( int[] numbers ){
    int[] right = new int[numbers - (numbers.length/2)];
    for ( int i = numbers.length/2; i < right.length; i++ ){
        right[i] = numbers[i];
    }
    return right[i];
}

public int[] merge( int[] numbers, int[] leftHalf, int[] rightHalf ){
    int left  = 0;
    int right = 0;
    for( int i = 0; i< numbers.length; i++){
        if( right>rightHalf.length || ( left < leftHalf.length && leftHalf[left]<=rightHalf[right] ) ){
            result[i] = leftHalf[left];
            left++;           
        } else{
            result[i] = rightHalf[right];
            right++;
        }
    }
    return result;
}