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CloneGraph.java
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77 lines (66 loc) · 2.13 KB
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package algorithm.lc;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
/**
* 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 #.
*
* First node is labeled as 0. Connect node 0 to both nodes 1 and 2. Second node
* is labeled as 1. Connect node 1 to node 2. 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 / \ \_/
*
*
*/
public class CloneGraph {
class UndirectedGraphNode {
int label;
ArrayList<UndirectedGraphNode> neighbors;
UndirectedGraphNode(int x) {
label = x;
neighbors = new ArrayList<UndirectedGraphNode>();
}
};
public class Solution {
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
// Note: The Solution object is instantiated only once and is reused by
// each test case.
if (node == null) {
return null;
}
Map<Integer, UndirectedGraphNode> visited = new HashMap<Integer, UndirectedGraphNode>();
return copy(node, visited);
}
private UndirectedGraphNode copy(UndirectedGraphNode node,
Map<Integer, UndirectedGraphNode> visited) {
if (node == null) {
return null;
}
UndirectedGraphNode newNode = visited.get(node.label); // find existing
// new node
if (newNode != null) {
return newNode;
}
newNode = new UndirectedGraphNode(node.label);
visited.put(node.label, newNode); // add new node to index
for (UndirectedGraphNode neighbor : node.neighbors) {
newNode.neighbors.add(copy(neighbor, visited));
}
return newNode;
}
}
}