net.sourceforge.cilib.entity.topologies.VonNeumannNeighbourhood Maven / Gradle / Ivy

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package net.sourceforge.cilib.entity.topologies;

import com.google.common.collect.Lists;

import fj.F;
import fj.data.List;

public class VonNeumannNeighbourhood extends Neighbourhood {

    private E find(List list, int n, int r, int c) {
        return list.index(r * n + c);
    }

    @Override
    public List f(final List list, final E target) {
        final int np = list.length();
        final int index = Lists.newArrayList(list).indexOf(target);
        final int sqSide = (int) Math.round(Math.sqrt(np));
        final int nRows = (int) Math.ceil(np / (double) sqSide);
        final int row = index / sqSide;
        final int col = index % sqSide;

        final F colsInRow = new F() {
            @Override
            public Integer f(Integer r) {
                return r == nRows - 1 ? np - r * sqSide : sqSide;
            }
        };

        final E north = find(list, sqSide, (row - 1 + nRows) % nRows - ((col >= colsInRow.f((row - 1 + nRows) % nRows)) ? 1 : 0), col);
        final E south = find(list, sqSide, (row + 1) % nRows - ((col >= colsInRow.f((row + 1) % nRows)) ? sqSide : 0), col);
        final E east = find(list, sqSide, row, (col + 1) % colsInRow.f(row));
        final E west = find(list, sqSide, row, (col - 1 + colsInRow.f(row)) % colsInRow.f(row));

        return List.list(target, north, east, south, west);
    }
}