Baowen Leetcode Notes

Problem OverviewProblem DescriptionYou are given an array power representing the computational strength of $n$ servers. The objective is to make the array non-decreasing (where each element is greater

Problem OverviewThe goal is to calculate the total resource consumption of tasks selected through a specific termination process in Amazon’s Elastic Container Service (ECS). You are given an array res

🧠 Summary of ThoughtsIdeaTo solve this problem, we use Breadth-First Search (BFS) to traverse the binary tree level by level. We maintain a queue to store nodes for BFS traversal. For each level, we

🧠 Summary of ThoughtsIdeaUse level-order traversal (BFS) to process the tree level by level. For each level, record the last node because it represents the node visible from the right side. Steps Use

🧠 Summary of ThoughtsWe find p and q traverse from bottom to top, but it’s generally believe that we can only traverse from top to bottom. But how can we traverse from bottom to top? Although we cann

🧠 Summary of ThoughtsZigZag = alternate walking left and right Use Depth-First Search (DFS) to traverse the tree recursively. Track the current path length separately for left and right directi

🧠 Summary of ThoughtsMethod 1For every node in the tree, treat it as a starting point, and count how many downward paths from that node sum to the target. So the problem is divided into two parts:

🧠 Summary of Thoughts Precompute bit counts using a HashMap Convert int[] to Integer[], since Arrays.sort() with a custom Comparator does NOT work on primitive int[] Sort using a custom Comparator Co

Question:Given an array of observed ids and a threshold, an ID is considered “active” (unavailable) if its frequency is ≥ threshold. If its frequency is < threshold, it is eligible for reuse. Yo

🧠 思路总结 Q: 为什么要单独写一个 helper 方法？ 因为题目函数 goodNodes(root) 只给一个参数，但 DFS 需要两个参数 (当前节点, 当前路径最大值)。 ✅ 代码（Java）123456789101112131415161718192021222324252627282930313233/** * Definition for a binary tree nod