刷题记录帖

378. Kth Smallest Element in a Sorted Matrix
practice tomorrow
441. Arranging Coins
done
287. Find the Duplicate Number
dont understand cycle detection
142. Linked List Cycle II
similiar
981. Time Based Key-Value Store
study tomorrow.

981. Time Based Key-Value Store
comparater
treemap

378. Kth Smallest Element in a Sorted Matrix
have bug why?

74. Search a 2D Matrix
practice tomorrow
240. Search a 2D Matrix II
kan budong
300. Longest Increasing Subsequence
392. Is Subsequence
why? I cannot get it?
528. Random Pick with Weight
study tmr

528. Random Pick with Weight
https://www.geeksforgeeks.org/generating-random-numbers-in-java/
https://www.cnblogs.com/grandyang/p/9784690.html
followup
https://leetcode.com/problems/ra ... hange-weights-array
https://www.geeksforgeeks.org/bi ... -or-fenwick-tree-2/


sum
https://www.cnblogs.com/grandyang/p/6854825.html

441. Arranging Coins
brute force: from idea to implementation?
what is the process?
think tmr

349. Intersection of Two Arrays
binary search: how?why?
Java.util.Arrays.binarySearch() Method


475. Heaters
idea: it is similiar to koko eat banana. the problem now is that how can i find a way to check weather a radius is applicable?
iterate through each house, find the nearest heater, check if distance of them are smaller than radius.
how to find the nearest heater?


367. Valid Perfect Square
那么我最先想出的方法是这样的，比如一个数字 49，我们先对其除以2，得到 24，发现 24 的平方大于 49，那么再对 24 除以2，得到 12，发现 12 的平方还是大于 49，再对 12 除以2，得到6，发现6的平方小于 49，于是遍历6到 12 中的所有数，看有没有平方等于 49 的，有就返回 true，没有就返回 false，

how to implement?

69. Sqrt(x)

303. Range Sum Query - Immutable
354. Russian Doll Envelopes
DP
611. Valid Triangle Number

475. Heaters
idea: it is similiar to koko eat banana. the problem now is that how can i find a way to check weather a radius is applicable?
iterate through each house, find the nearest heater, check if distance of them are smaller than radius.
how to find the nearest heater?


java.util.Arrays.binarySearch(Object[] a, Object key)

This method returns index of the search key, if it is contained in the array, else it returns (-(insertion point) - 1). The insertion point is the point at which the key would be inserted into the array: the index of the first element greater than the key, or a.length if all elements in the array are less than the specified key.

https://www.geeksforgeeks.org/treeset-in-java-with-examples/
practice tomorrow

410. Split Array Largest Sum 分割数组的最大值
how  to convert from idea to implementation
practice tmr

周五休息

周六：
group study
410. Split Array Largest Sum
understand it and practice
1237. Find Positive Integer Solution for a Given Equation
binary search
for(int x=1; x<=1000; x++){
            int low=1, high =1000;
            while(low<=high){
                int mid = low+(high-low)/2;
                if(customfunction.f(x,mid)>z){
                     high = mid-1;
                }else if(customfunction.f(x, mid)<z){
                    low = mid+1;
                }else{
                    ans.add(Arrays.asList(x,mid));
                    break;//be careful with this part. TLE
                }
            }
        }
Equals and hashcode I dont understand.
https://www.geeksforgeeks.org/equals-hashcode-methods-java/
https://zhuanlan.zhihu.com/p/30321358

36. Valid Sudoku
37. Sudoku Solver
773. Sliding Puzzle
BFS
227. Basic Calculator II yixilie
think about the process

what is DFS
https://www.geeksforgeeks.org/de ... or-dfs-for-a-graph/

Iterator
https://www.geeksforgeeks.org/how-to-use-iterator-in-java/
https://www.geeksforgeeks.org/graph-and-its-representations/

886. Possible Bipartition
785. Is Graph Bipartite?