刷题 - 随笔分类(第2页) - CasperWin

30 Day Challenge Day 18 | Leetcode 200. Number of Islands (BFS)

摘要：题解 Medium 用BFS再做了一遍。 class Solution { public: int numIslands(vector<vector<char>>& grid) { if(grid.empty()) return 0; int count = 0; vector<vector<boo 阅读全文

posted @ 2020-10-03 03:44 CasperWin 阅读(94) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 261. Graph Valid Tree

摘要：题解 Medium BFS 一个节点只计算一次，这一点要注意。 class Solution { public: bool validTree(int n, vector<vector<int>>& edges) { vector<unordered_set<int>> graph(n, unord 阅读全文

posted @ 2020-10-02 14:17 CasperWin 阅读(68) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 559. Maximum Depth of N-ary Tree

摘要：题解 Easy | BFS 典型的求最大深度，用BFS。 class Solution { public: int maxDepth(Node* root) { if(!root) return 0; queue<Node*> q; q.push(root); int max_depth = 0; 阅读全文

posted @ 2020-10-02 13:37 CasperWin 阅读(87) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 133. Clone Graph

摘要：题解 Medium BFS Deep Copy 的一个例子。 class Solution { public: Node* cloneGraph(Node* node) { if(!node) return nullptr; unordered_map<Node*, Node*> m; Node* 阅读全文

posted @ 2020-10-02 13:22 CasperWin 阅读(78) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 126. Word Ladder II

摘要：题解 Hard 难死了。 class Solution { public: vector<vector<string>> findLadders(string beginWord, string endWord, vector<string>& wordList) { unordered_set<s 阅读全文

posted @ 2020-10-02 12:55 CasperWin 阅读(66) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 489. Robot Room Cleaner

摘要：题解 Hard BFS class Solution { public: void cleanRoom(Robot& robot) { dfs(robot, 0, 0, 0); } void goback(Robot &r) { r.turnLeft(); r.turnLeft(); r.move( 阅读全文

posted @ 2020-10-02 11:37 CasperWin 阅读(110) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 127. Word Ladder

摘要：题解 Medium 方法：BFS class Solution { public: int ladderLength(string beginWord, string endWord, vector<string>& wordList) { int steps = 0; unordered_set< 阅读全文

posted @ 2020-10-02 09:24 CasperWin 阅读(98) 评论(0) 推荐(0)

30 Day Challenge Day 17 | Leetcode 624. Maximum Distance in Arrays

摘要：题解 Easy 我倒是觉得不太容易，即使看了答案，也不确定这是令人信服的解法。直到看了动态图的讲解，所以还是画图更直观。 class Solution { public: int maxDistance(vector<vector<int>>& arrays) { int res = 0, min_ 阅读全文

posted @ 2020-10-02 07:53 CasperWin 阅读(136) 评论(0) 推荐(0)

30 Day Challenge Day 16 | Leetcode 701. Insert into a Binary Search Tree

摘要：题解 Hard 方法：Trie struct TrieNode { vector<int> indexes; vector<TrieNode*> next; TrieNode() : next(26, nullptr) { } }; class Solution { public: vector<v 阅读全文

posted @ 2020-10-01 07:47 CasperWin 阅读(103) 评论(0) 推荐(0)

30 Day Challenge Day 16 | Leetcode 692. Top K Frequent Words

摘要：题解 Medium Heap (Priority Queue) 难点是自己写comparator。 class comparator { public: bool operator() (const pair<string, int>& a, const pair<string, int>& b) 阅读全文

posted @ 2020-10-01 06:50 CasperWin 阅读(96) 评论(0) 推荐(0)

30 Day Challenge Day 16 | Leetcode 210. Course Schedule II

摘要：题解 Medium Topological Sort class Solution { public: vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) { vector<vector<int>> gr 阅读全文

posted @ 2020-10-01 05:52 CasperWin 阅读(89) 评论(0) 推荐(0)

30 Day Challenge Day 16 | Leetcode 207. Course Schedule

摘要：题解 Medium 方法：Topological Sort class Solution { public: bool canFinish(int numCourses, vector<vector<int>>& prerequisites) { vector<vector<int>> graph( 阅读全文

posted @ 2020-10-01 05:42 CasperWin 阅读(92) 评论(0) 推荐(0)

30 Day Challenge Day 15 | Leetcode 257. Binary Tree Paths

摘要：题解 Easy | DFS class Solution { public: vector<string> binaryTreePaths(TreeNode* root) { vector<string> paths; dfs(root, "", paths); return paths; } vo 阅读全文

posted @ 2020-09-30 14:53 CasperWin 阅读(76) 评论(0) 推荐(0)

30 Day Challenge Day 15 | Leetcode 113. Path Sum II

摘要：题解 Medium | DFS class Solution { public: vector<vector<int>> pathSum(TreeNode* root, int sum) { vector<vector<int>> paths; vector<int> path; dfs(root, 阅读全文

posted @ 2020-09-30 14:44 CasperWin 阅读(68) 评论(0) 推荐(0)

30 Day Challenge Day 15 | Leetcode 329. Longest Increasing Path in a Matrix

摘要：题解 Hard 方法一：DFS + Memoization class Solution { public: int longestIncreasingPath(vector<vector<int>>& matrix) { if(matrix.empty()) return 0; m = matri 阅读全文

posted @ 2020-09-30 14:27 CasperWin 阅读(89) 评论(0) 推荐(0)

30 Day Challenge Day 15 | Leetcode 720. Longest Word in Dictionary

摘要：题解 Easy 方法一：Greedy 贪心算法 class Solution { public: string longestWord(vector<string>& words) { string res; unordered_set<string> s; sort(words.begin(), 阅读全文

posted @ 2020-09-30 13:26 CasperWin 阅读(80) 评论(0) 推荐(0)

30 Day Challenge Day 15 | Leetcode 100. Same Tree

摘要：题解 Easy | Tree, DFS class Solution { public: bool isSameTree(TreeNode* p, TreeNode* q) { if(!p && !q) return true; if(!p || !q) return false; if(p->va 阅读全文

posted @ 2020-09-30 12:25 CasperWin 阅读(78) 评论(0) 推荐(0)

30 Day Challenge Day 15 | Leetcode 112. Path Sum

摘要：题解 Easy | Tree, DFS class Solution { public: bool hasPathSum(TreeNode* root, int sum) { if(!root) return false; if(!root->left && !root->right) return 阅读全文

posted @ 2020-09-30 12:04 CasperWin 阅读(60) 评论(0) 推荐(0)

30 Day Challenge Day 14 | Leetcode 167. Two Sum II - Input array is sorted

摘要：题解 Easy | Hashmap class Solution { public: vector<int> twoSum(vector<int>& numbers, int target) { unordered_map<int, int> m; for(int i = 0; i < number 阅读全文

posted @ 2020-09-29 13:31 CasperWin 阅读(55) 评论(0) 推荐(0)

30 Day Challenge Day 14 | Leetcode 90. Subsets II

摘要：题解 Medium | Backtracking class Solution { public: vector<vector<int>> subsetsWithDup(vector<int>& nums) { sort(nums.begin(), nums.end()); vector<vecto 阅读全文

posted @ 2020-09-29 12:58 CasperWin 阅读(101) 评论(0) 推荐(0)

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