具有多个值的java转换映射到树？

Question

给定一组随机分布的键，每个键映射到一组值，如何将其转换为多棵树

示例数据集

• 注意；{NC₂ND₂}
  
• ND₁=>；{NG₁NH₁}
  
• NA₁=>；{NB₁}
• 注意：1；{NC₁ND₁NE₁}
  
• NA₂=>；{NB₂}
  
• NC₁=>；{NF₁}
  
• NE₁=>；{NI₁NJ₁NK₁}
  

NA_{1的结果树}

NA1
`-- NB1
    |-- NC1
    |   `-- NF1
    |-- ND1
    |   |-- NG1
    |   `-- NH1
    `-- NE1
        |-- NI1
        |-- NJ1
        `-- NK1

NA_{2的结果树}

NA2
`-- NB2
    |-- NC2
    `-- ND2

Answer 1

我不知道有任何库方法可以进行这种转换。我会这么做的。这很简单，依我看

public class Tree {
    public Tree(String key) {
        // ...
    }
    public void addChild(Tree child) {
        // ...
    }
}

public Set<Tree> transform(Map<String, List<String>> input) {
    // Potential tree roots.  We start with all LHS keys as potential roots,
    // and eliminate them when we see their keys on the RHS.
    Set<String> roots = new HashSet<String>(input.keySet());

    // This map associates keys with the tree nodes that we create for them
    Map<String, Tree> map = new HashMap<String, Tree>();

    for (Map.Entry<String, List<String>> entry : input.entrySet()) {
        String key = entry.getKey();
        List<String> childKeys = entry.getValue();
        Tree tree = map.get(key);
        if (tree == null) {
            tree = new Tree(key);
            map.put(key, tree);
        }
        for (String childKey : childKeys) {
            roots.remove(childKey);
            Tree child = map.get(childKey);
            if (child == null) {
                child = new Tree(childKey);
                map.put(childKey, child);
            }
            tree.addChild(child);
        }
    }
    Set<Tree> res = new HashSet<Tree>(roots.size());
    for (String key : roots) {
        res.add(map.get(key));
    }
    return res;
}

编辑：注意，如果输入代表一组DAG（有向无环图），该算法将“起作用”。然而，我刚刚意识到，生成的一组树将共享输入数据中任何公共子树的TreeNode实例

请注意，我尚未调试此代码：-）