Google S2 算法 Java 操作

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获取指定子级的全部Cell

/*** 获取指定级别的全部子cell** @param root     当前cellId* @param desLevel 目标level, > root.level()*/public List<S2CellId> children(S2CellId root, int desLevel) {if (root.level() < desLevel) {long interval = (root.childEnd().id() - root.childBegin().id()) / 4;List<S2CellId> list = new ArrayList<>();for (int i = 0; i < 4; i++) {long id = root.childBegin().id() + interval * i;S2CellId cellId = new S2CellId(id);List<S2CellId> childrenCellId = children(cellId, desLevel);list.addAll(childrenCellId);}return list;} else if (root.level() == desLevel) {return Collections.singletonList(root);} else {return Collections.emptyList();}}

获取指定子级的边界Cell

/*** 获取指定子级的边界Cell（当前cell内部）* * @param s2CellId 当前cellId* @param desLevel 目标cellId的level 需大于当前cellId*/
public List<S2CellId> childrenCellId(S2CellId root, S2CellId s2CellId, int desLevel) throws IOException {if (s2CellId.level() < desLevel - 1) {long interval = (s2CellId.childEnd().id() - s2CellId.childBegin().id()) / 4;List<S2CellId> list = new ArrayList<>();for (int i = 0; i < 4; i++) {long id = s2CellId.childBegin().id() + interval * i;S2CellId cellId = new S2CellId(id);S2CellId[] neighbors = new S2CellId[4];cellId.getEdgeNeighbors(neighbors);boolean edge = Arrays.stream(neighbors).anyMatch(neighbor -> !root.contains(neighbor));if (edge) {List<S2CellId> childrenCellId = childrenCellId(root, cellId, desLevel);list.addAll(childrenCellId);}}return list;} else if (s2CellId.level() == desLevel - 1) {long interval = (s2CellId.childEnd().id() - s2CellId.childBegin().id()) / 4;List<S2CellId> list = new ArrayList<>();for (int i = 0; i < 4; i++) {long id = s2CellId.childBegin().id() + interval * i;S2CellId cellId = new S2CellId(id);S2CellId[] neighbors = new S2CellId[4];cellId.getEdgeNeighbors(neighbors);boolean edge = Arrays.stream(neighbors).anyMatch(neighbor -> !root.contains(neighbor));if (edge) {list.add(cellId);}}return list;}return Collections.emptyList();}

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