Leetcode 133：Clone Graph

最新推荐文章于 2020-01-14 22:58:04 发布

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最新推荐文章于 2020-01-14 22:58:04 发布

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Given a reference of a node in a connected undirected graph, return a deep copy (clone) of the graph. Each node in the graph contains a val (int) and a list (List[Node]) of its neighbors.

Example:
在这里插入图片描述
Input:
{“ $KaTeX parse error: Expected '}', got 'EOF' at end of input: \dots"neighbors":[{"$ id”:“2”,“neighbors”:[{“ $KaTeX parse error: Expected 'EOF', got '}' at position 9: ref":"1"}̲,{"$ id”:“3”,“neighbors”:[{“ $KaTeX parse error: Expected 'EOF', got '}' at position 9: ref":"2"}̲,{"$ id”:“4”,“neighbors”:[{“ $KaTeX parse error: Expected 'EOF', got '}' at position 9: ref":"3"}̲,{"$ ref”:“1”}],“val”:4}],“val”:3}],“val”:2},{"$ref":“4”}],“val”:1}

Explanation:
Node 1’s value is 1, and it has two neighbors: Node 2 and 4.
Node 2’s value is 2, and it has two neighbors: Node 1 and 3.
Node 3’s value is 3, and it has two neighbors: Node 2 and 4.
Node 4’s value is 4, and it has two neighbors: Node 1 and 3.

Note:

1.The number of nodes will be between 1 and 100.
2.The undirected graph is a simple graph, which means no repeated edges and no self-loops in the graph.
3.Since the graph is undirected, if node p has node q as neighbor, then node q must have node p as neighbor too.
4.You must return the copy of the given node as a reference to the cloned graph.

C++
  Node* cloneGraph(Node* node) {
        unordered_map<Node*,Node*> m;
        return helper(node,m);
    }
    Node* helper(Node* node,unordered_map<Node*,Node*>& m)
    {
        if(!node)
            return nullptr;
        if(m.count(node))return m[node];
        Node* clone = new Node(node->val);
        m[node] = clone;
        for(auto neighbor : node->neighbors)
        {
            clone->neighbors.push_back(helper(neighbor,m));
        }
        return clone;
    }