Algorithms—133.Balanced Binary Tree

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思路：首先遍历所有的元素，添加到map中，然后读取map，给每个元素编号，放进list中，同时新建list存储每个复制了lable的元素。最后读取原list，查看该list每个邻居，去map中查看这些邻居的编号，去新list中找到对应的邻居，添加到对应的元素的邻居中。

/** * 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) {    Map<UndirectedGraphNode, Integer> initMap=f(node,new HashMap<UndirectedGraphNode, Integer>());    Map<UndirectedGraphNode, Integer> map=new HashMap<UndirectedGraphNode, Integer>();    map.put(node, 0);    List<UndirectedGraphNode> list=new ArrayList<UndirectedGraphNode>();    list.add(node);    List<UndirectedGraphNode> ans=new ArrayList<UndirectedGraphNode>();    UndirectedGraphNode init=new UndirectedGraphNode(node.label);    ans.add(init);    int k=1;    for (UndirectedGraphNode ugn : initMap.keySet()) {    if (ugn!=node) {map.put(ugn, k);list.add(ugn);ans.add(new UndirectedGraphNode(ugn.label));k++;}    }    for (int i = 0; i < list.size(); i++) {List<UndirectedGraphNode> neis=list.get(i).neighbors;UndirectedGraphNode u=ans.get(i);for (int j = 0; j < neis.size(); j++) {u.neighbors.add(ans.get(map.get(neis.get(j))));}}    return init;}    return null;    }    public Map<UndirectedGraphNode, Integer> f(UndirectedGraphNode node,Map<UndirectedGraphNode, Integer> map){    if (node!=null&&map.get(node)==null) {    map.put(node, 1);    List<UndirectedGraphNode> list=node.neighbors;    if (list!=null) {for (int i = 0; i < list.size(); i++) {map=f(list.get(i),map);}}}    return map;    }}

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