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LeetCode: 133. Clone Graph


LeetCode: 133. Clone Graph

题目描述

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

OJ’s undirected graph serialization:
Nodes are labeled uniquely.
We use ​​​#​​​ as a separator for each node, and ​​,​​​ as a separator for node label and each neighbor of the node.
As an example, consider the serialized graph ​​​{0,1,2#1,2#2,2}​​.

The graph has a total of three nodes, and therefore contains three parts as separated by ​​#​​.

  1. First node is labeled as ​​0​​​. Connect node ​​0​​​ to both nodes ​​1​​​ and ​​2​​.
  2. Second node is labeled as ​​1​​​. Connect node ​​1​​​ to node ​​2​​.
  3. Third node is labeled as ​​2​​​. Connect node ​​2​​​ to node ​​2​​ (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

1
/ \
/ \
0 --- 2
/ \
\_/

解题思路 —— 递归分治

记录复制过的,正在复制的节点, 递归地处理每一个没有处理过的节点。

AC代码

/**
* Definition for undirected graph.
* struct UndirectedGraphNode {
* int label;
* vector<UndirectedGraphNode *> neighbors;
* UndirectedGraphNode(int x) : label(x) {};
* };
*/
class Solution {
public:
UndirectedGraphNode *cloneGraphRef(UndirectedGraphNode *node,
map<int, UndirectedGraphNode*>& recordedNode) {

if(node == nullptr) return nullptr;
if(recordedNode.find(node->label) != recordedNode.end())
{
return recordedNode[node->label]; // 已经处理过, 直接返回存储的值
}

UndirectedGraphNode* pCurNode = new UndirectedGraphNode(node->label);
// 记录当前的节点
recordedNode[pCurNode->label] = pCurNode;

// 分治:分别处理每一个 neighbors 节点
for(size_t i = 0; i < node->neighbors.size(); ++i)
{
pCurNode->neighbors.push_back(cloneGraphRef(node->neighbors[i], recordedNode));
}

return pCurNode;
}

UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
map<int, UndirectedGraphNode*> recordedNode;
return cloneGraphRef(node, recordedNode);
}
};


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