133. Clone Graph

Description

image-20210811000504275

133-2

133-4133-3

Solution

I uses two map to store the visited and waiting nodes, then BFS for the next node be copied.

Code

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/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> neighbors;
    Node() {
        val = 0;
        neighbors = vector<Node*>();
    }
    Node(int _val) {
        val = _val;
        neighbors = vector<Node*>();
    }
    Node(int _val, vector<Node*> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
};
*/

class Solution {
    unordered_map<int, Node*> visited;
    unordered_map<int, Node*> waited;
public:
    Node* cloneGraph(Node* node) {
        if(node == nullptr)
            return node;
        queue<Node*> q;
        Node* root = new Node(node->val, node->neighbors);
        q.push(root);
        waited[root->val] = root;
        while(!q.empty()){
            int size = q.size();
            for(int i = 0; i < size; i++){
                auto top = q.front();
                q.pop();
                for(int i = 0; i < top->neighbors.size(); i ++){
                    auto nbor = top->neighbors[i];
                    if(visited.find(nbor->val) == visited.end()){
                        Node *next = nullptr;
                        if(waited.find(nbor->val) == waited.end()){
                            next = new Node(nbor->val, nbor->neighbors);
                            waited[nbor->val] = next;
                        }else
                            next = waited[nbor->val];
                        top->neighbors[i] = next;
                        q.push(top->neighbors[i]);
                    }else{
                        top->neighbors[i] = visited[nbor->val];
                    }
                }
                visited[top->val] = top;
                waited.erase(top->val);
            }
        }
        return root;
    }
};

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