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Copy pathClone Graph.java
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Copy pathClone Graph.java
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77 lines (67 loc) · 2.96 KB
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/*
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
/ \
\_/
Hide Tags Depth-first Search Breadth-first Search Graph
Thinking process:
1. Clone all nodes available: using HashMap to go through all possible query. No duplicates added using HashMap.
HashMap map has the list of all new nodes. No neighbors added yet
<key,value> = <original node, new node with just a label (without neighbor list)>
At same time, the arrayList nodes has all original nodes(with neighbors) in Breadth-first order.
2. Add neighbor for nodes in map:
- Locate the 'newNode' from map by using the key: the original node
- loop through the original node's neighbor size
- use original neighbor as key to get the new neighbor instance from map
- add this new neighbor instance to the neighbor list of 'newNode'
*/
/**
* Definition for undirected graph.
* class UndirectedGraphNode {
* int label;
* List<UndirectedGraphNode> neighbors;
* UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
* };
*/
public class Solution {
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
if (node == null) {
return node;
}
ArrayList<UndirectedGraphNode> nodes = new ArrayList<UndirectedGraphNode>();
nodes.add(node);
HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
map.put(node, new UndirectedGraphNode(node.label));
int start = 0;
//Clone nodes without neighbors:
while (start < nodes.size()) {
List<UndirectedGraphNode> neighbors = nodes.get(start++).neighbors;
for (int i = 0; i < neighbors.size(); i++) {
if (!map.containsKey(neighbors.get(i))) {
map.put(neighbors.get(i), new UndirectedGraphNode(neighbors.get(i).label));
nodes.add(neighbors.get(i));
}
}
}
// Clone neighbors:
for (int i = 0; i < nodes.size(); i++) {
UndirectedGraphNode newNode = map.get(nodes.get(i));
for (int j = 0; j < nodes.get(i).neighbors.size(); j++) {
newNode.neighbors.add(map.get(nodes.get(i).neighbors.get(j)));
}
}
return map.get(node);
}
}