abstract String getName();

abstract Layer[] sort(Layer[] layers);

/**

* Creates a 'top' and 'bottom' collection.

* Iterating through the previously sorted list of layers, place each layer

* in whichever collection has less total mass, arriving at an evenly

* weighted graph. Reassemble such that the layers that appeared earliest

* end up in the 'center' of the graph.

*/

protected Layer[] orderToOutside(Layer[] layers) {

int j = 0;

int n = layers.length;

Layer[] newLayers = new Layer[n];

int topCount = 0;

float topSum = 0;

int[] topList = new int[n];

int botCount = 0;

float botSum = 0;

int[] botList = new int[n];

// partition to top or bottom containers

for (int i=0; i<n; i ) {

if (topSum < botSum) {

topList[topCount ] = i;

topSum = layers[i].sum;

} else {

botList[botCount ] = i;

botSum = layers[i].sum;

}

}

// reassemble into single array

for (int i = botCount - 1; i >= 0; i--) {

newLayers[j ] = layers[botList[i]];

}

for (int i = 0; i < topCount; i ) {

newLayers[j ] = layers[topList[i]];

}

return newLayers;

}