來源是：id, pid,name1, 0, a2, 1, b3, 1, c我們預期的結果是：id,pid,name,upnum,uplevel,downum,downlevel1, 0, a, 0, 0, 2, 1 2, 1, b, 1, 1, 0, 03, 1, c, 1, 1, 0, 0在這里，名字是人的名字，id標識每個人，pid表示父母id，例如，人a是人b的上級。upnum表示他總共有多少上級，上層表示他有多少級上級，下級和下級幾乎像這樣為了得到這個結果，我想我有兩種方式1.使用數據庫，像口服，我使用和，一切都很好。但是對于每個人來說，我必須再次運行“連接”sql，這似乎很慢。而且我們必須在客戶端安裝預言機，有些客戶端不喜歡它。如果我們使用h2或一些嵌入式數據庫，我們可以使用oracle中的功能嗎？但我想它也很慢。或者我們應該做id的索引？connect bynocyclenocycle2.使用java hashMap來存儲id和pid的關系，但是當數據變大時，可能會出現內存不足異常。如何編寫代碼？最好的方法是什么？還是有更好的方法？比如一些圖形算法，或者graph-db（數據庫）？
1 回答
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TA貢獻1802條經驗 獲得超5個贊
沒有真正需要數據庫。一個簡單的迭代和一個遞歸函數可以做所需的分析：
import java.util.ArrayList;
import java.util.List;
public class Graph {
private final List<Node> nodes;
private final Node root;
//Graph assumes unique id > 0, and only root with pid = 0
Graph(Node root){
this.root = root;
nodes = new ArrayList<>();
nodes.add(root);
};
void add(Node node){
nodes.add(node);
}
void analyze(){
//sort by pid so iteration goes from top level down
nodes.sort( (n1,n2) -> Integer.compare(n1.getPid(), n2.getPid()) );
for(Node node : nodes){
Node parent = getNode(node.getPid());
if (parent == null ) {
continue; //skip root
}
node.setUpLevel(parent.getUpLevel()+1); //add 1 to parent value
node.setUpNum(node.getUpNum() +1); //increment by 1
parent.setDowNum(parent.getDowNum() +1); //increment by 1
updateHigherLevels(node);
}
}
//recursively update higher levels
private void updateHigherLevels(Node node) {
Node parent = getNode(node.getPid());
if(parent == null) return;
parent.setDownLevel(node.getDownLevel() + 1);
updateHigherLevels(parent);
}
void print(){
//sort by id for nice printing
nodes.sort( (n1,n2) -> Integer.compare(n1.getId(), n2.getId()) );
String format = "\n%2s %3s %4s %5s %7s %7s %8s";
System.out.printf(format,"id","pid","name","upnum","uplevel", "downnum" , "downlevel");
for(Node node : nodes){
System.out.printf(format, node.getId(), node.getPid(), node.getName(), node.getUpNum(), node.getUpLevel()
, node.getDowNum(), node.getDownLevel());
}
}
Node getNode(int id){
for(Node node : nodes){
if(node.getId() == id) return node;
}
return null;
}
public static void main(String[] args) {
//make graph
Graph graph = new Graph(new Node(1, 0, "a"));
graph.add(new Node(2, 1, "b"));
graph.add(new Node(3, 1, "c"));
graph.add(new Node(4, 2, "d"));
graph.add(new Node(5, 2, "e"));
graph.analyze();
graph.print();
}
}
class Node {
private final int id,pid;
private int upnum = 0, uplevel = 0, downum = 0, downlevel = 0;
private final String name;
Node(int id, int pid, String name) {
super();
this.id = id;
this.pid = pid;
this.name = name;
}
int getId() { return id; }
int getPid() { return pid; }
String getName() { return name; }
int getUpNum() { return upnum; }
void setUpNum(int upnum) { this.upnum = upnum; }
int getUpLevel() { return uplevel; }
void setUpLevel(int uplevel) { this.uplevel = uplevel; }
int getDowNum() { return downum; }
void setDowNum(int downum) { this.downum = downum; }
int getDownLevel() { return downlevel; }
void setDownLevel(int downlevel) { this.downlevel = downlevel; }
}
輸出：
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