# [LeetCode] Clone Graph 克隆无向图,LeetCode All in One 题目讲解汇总(持续更新中...)

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:

```Input:
{"\$id":"1","neighbors":[{"\$id":"2","neighbors":[{"\$ref":"1"},{"\$id":"3","neighbors":[{"\$ref":"2"},{"\$id":"4","neighbors":[{"\$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.

```class Solution {
public:
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 NULL;
if (m.count(node)) return m[node];
Node *clone = new Node(node->val);
m[node] = clone;
for (Node *neighbor : node->neighbors) {
clone->neighbors.push_back(helper(neighbor, m));
}
return clone;
}
};```

```class Solution {
public:
Node* cloneGraph(Node* node) {
if (!node) return NULL;
unordered_map<Node*, Node*> m;
queue<Node*> q{{node}};
Node *clone = new Node(node->val);
m[node] = clone;
while (!q.empty()) {
Node *t = q.front(); q.pop();
for (Node *neighbor : t->neighbors) {
if (!m.count(neighbor)) {
m[neighbor] = new Node(neighbor->val);
q.push(neighbor);
}
m[t]->neighbors.push_back(m[neighbor]);
}
}
return clone;
}
};```

Copy List with Random Pointer

https://leetcode.com/problems/clone-graph/

https://leetcode.com/problems/clone-graph/discuss/42313/C%2B%2B-BFSDFS

https://leetcode.com/problems/clone-graph/discuss/42309/Depth-First-Simple-Java-Solution

LeetCode All in One 题目讲解汇总(持续更新中…)

原文作者：Grandyang
原文地址: https://www.cnblogs.com/grandyang/p/4267628.html
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