【LeetCode】图论 graph（共20题）

【133】Clone Graph （2019年3月9日，复习）

给定一个图，返回它的深拷贝。

题解：dfs 或者 bfs 都可以

 /*
 // Definition for a Node.
 class Node {
 public:
     int val;
     vector<Node*> neighbors;
 
     Node() {}
 
     Node(int _val, vector<Node*> _neighbors) {
         val = _val;
         neighbors = _neighbors;
     }
 };
 */
 class Solution {
 public:
     Node* cloneGraph(Node* node) {
         if (!node) {return node;}
         unordered_map<Node*, Node*> memo;
         Node* copy = new Node(node->val,  vector<Node*>{});
         memo[node] = copy;
         queue<Node*> que;
         que.push(node);
         unordered_set<Node*> visit;
         visit.insert(node);
         while (!que.empty()) {
             Node* cur = que.front(); que.pop();
             Node* copyCur = memo[cur];
             for (auto& adj : cur->neighbors) {
                 if (memo.find(adj) == memo.end()) {
                     Node* copyAdj = new Node(adj->val, vector<Node*>{});
                     memo[adj] = copyAdj;
                 }
                 copyCur->neighbors.push_back(memo[adj]);
                 if (visit.find(adj) == visit.end()) {
                     visit.insert(adj);
                     que.push(adj);
                 }
             }
         }
         return copy;
     }
 };

【207】Course Schedule

【210】Course Schedule II

【261】Graph Valid Tree

【269】Alien Dictionary

【310】Minimum Height Trees

【323】Number of Connected Components in an Undirected Graph

【332】Reconstruct Itinerary

【399】Evaluate Division

【444】Sequence Reconstruction

【684】Redundant Connection

【685】Redundant Connection II

【743】Network Delay Time

【765】Couples Holding Hands

【785】Is Graph Bipartite?

【802】Find Eventual Safe States

【839】Similar String Groups

【841】Keys and Rooms

【854】K-Similar Strings

【928】Minimize Malware Spread II