[leetcode] clone graph

典型DFS题目。。用一个HashMap把已经clone过的node记住... 要是遇到了 就不进行克隆过程 直接拿来用

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public class Solution { HashMap<UndirectedGraphNode, UndirectedGraphNode> visited = new HashMap<UndirectedGraphNode, UndirectedGraphNode>(); public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) { if (node == null){ return null; } UndirectedGraphNode root = dfsCopy(node); return root; } private UndirectedGraphNode dfsCopy(UndirectedGraphNode node){ if (visited.containsKey(node)){ return visited.get(node); } UndirectedGraphNode root = new UndirectedGraphNode(node.label); visited.put(node, root); for (int i = 0; i < node.neighbors.size(); i++){ root.neighbors.add(dfsCopy(node.neighbors.get(i))); } return root; } }