LeetCode-Clone Graph

最新推荐文章于 2022-01-22 13:53:54 发布

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#leetcode #Clone Graph

Cracking LeetCode 同时被 3 个专栏收录

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本文详细介绍了无向图的克隆算法实现，包括序列化、哈希表使用及广度优先搜索策略，通过实例解析算法过程。

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:

Solution:

Code:

<span style="font-size:14px;">/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        if (node == NULL) return NULL;
        UndirectedGraphNode *copy = node;
        unordered_map<int, UndirectedGraphNode *> hashTable;
        queue<UndirectedGraphNode *> q;
        q.push(node);
        while (!q.empty()) {
            node = q.front();
            q.pop();
            if (hashTable.find(node->label) == hashTable.end()) {
                hashTable[node->label] = new  UndirectedGraphNode(node->label);
                for (int i = 0; i < node->neighbors.size(); ++i)
                    q.push(node->neighbors[i]);
            }
        }
        unordered_set<int> s;
        q.push(copy);
        while (!q.empty()) {
            node = q.front();
            q.pop();
            if (s.find(node->label) == s.end()) {
                s.insert(node->label);
                for (int i = 0; i < node->neighbors.size(); ++i) {
                    q.push(node->neighbors[i]);
                    hashTable[node->label]->neighbors.push_back(hashTable[node->neighbors[i]->label]);
                }
            }
        }
        return hashTable[copy->label];
    }
};</span>