Articles
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743 - Network Delay Time
There are N network nodes, labelled 1 to N. Given times, a list of travel times as directed edges times[i] = (u, v, w), where u is the source node, v is the target node, and w is the time it takes for a signal to travel from source to target. Now, we send a signal from a certain node K. How long will it take for all nodes to receive the signal? If it is impossible, return -1.
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729 - My Calender I
Implement a MyCalendar class to store your events. A new event can be added if adding the event will not cause a double booking. Your class will have the method, book(int start, int end). Formally, this represents a booking on the half open interval [start, end), the range of real numbers x such that start <= x < end. A double booking happens when two events have some non-empty intersection (ie., there is some time that is common to both events.) For each call to the method MyCalendar.book, return true if the event can be added to the calendar successfully without causing a double booking. Otherwise, return false and do not add the event to the calendar.
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731 - My Calendar II
Implement a MyCalendarTwo class to store your events. A new event can be added if adding the event will not cause a triple booking. Your class will have one method, book(int start, int end). Formally, this represents a booking on the half open interval [start, end), the range of real numbers x such that start <= x < end. A triple booking happens when three events have some non-empty intersection. For each call to the method MyCalendar.book, return true if the event can be added to the calendar successfully without causing a triple booking. Otherwise, return false and do not add the event to the calendar.
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939 - Minimum Area Rectangle
Given a set of points in the xy-plane, determine the minimum area of a rectangle formed from these points, with sides parallel to the x and y axes. If there isn’t any rectangle, return 0.
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846 - Hand Of Straights
Alice has a hand of cards, given as an array of integers. Now she wants to rearrange the cards into groups so that each group is size W, and consists of W consecutive cards. Return true if and only if she can.
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1145 - Binary Tree Coloring Game
Two players play a turn based game on a binary tree. We are given the root of this binary tree, and the number of nodes n in the tree. n is odd, and each node has a distinct value from 1 to n. Initially, the first player names a value x with 1 <= x <= n, and the second player names a value y with 1 <= y <= n and y != x. The first player colors the node with value x red, and the second player colors the node with value y blue. Then, the players take turns starting with the first player. In each turn, that player chooses a node of their color (red if player 1, blue if player 2) and colors an uncolored neighbor of the chosen node (either the left child, right child, or parent of the chosen node.) If (and only if) a player cannot choose such a node in this way, they must pass their turn. If both players pass their turn, the game ends, and the winner is the player that colored more nodes. You are the second player. If it is possible to choose such a y to ensure you win the game, return true. If it is not possible, return false.
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1074 - Numbers Of Submatrices That Sum To Target
Given a matrix and a target, return the number of non-empty submatrices that sum to target.
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727 - Minimum Window Subsequence
Given strings S and T, find the minimum (contiguous) substring W of S, so that T is a subsequence of W. If there is no such window in S that covers all characters in T, return the empty string “”. If there are multiple such minimum-length windows, return the one with the left-most starting index.
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801 - Minimum Swaps To Make Sequence Increasing
We have two integer sequences A and B of the same non-zero length. We are allowed to swap elements A[i] and B[i]. Note that both elements are in the same index position in their respective sequences. At the end of some number of swaps, A and B are both strictly increasing. (A sequence is strictly increasing if and only if A[0] < A[1] < A[2] < … < A[A.length - 1].) Given A and B, return the minimum number of swaps to make both sequences strictly increasing. It is guaranteed that the given input always makes it possible.
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1231 - Divide Chocolate
```python class Solution: def maximizeSweetness(self, sweetness: List[int], K: int) -> int: lo, hi = min(sweetness), sum(sweetness) while lo <= hi: mid = (lo + hi) // 2 if self.is_valid(sweetness, K, mid): hi = mid - 1 #1) divide the array into m parts and each part is larger than mid #2) fail to divide into m parts else: lo = mid + 1 return lo
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552 - Student Attendance Record Ii
Given a positive integer n, return the number of all possible attendance records with length n, which will be regarded as rewardable. The answer may be very large, return it after mod 109 + 7. A student attendance record is a string that only contains the following three characters. A record is regarded as rewardable if it doesn’t contain more than one ‘A’ (absent) or more than two continuous ‘L’ (late).
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1153 - String Transformations Into Another String
Given two strings str1 and str2 of the same length, determine whether you can transform str1 into str2 by doing zero or more conversions. In one conversion you can convert all occurrences of one character in str1 to any other lowercase English character. Return true if and only if you can transform str1 into str2. reference
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659 - Split Array Into Consecutive Subsequences
Given an array nums sorted in ascending order, return true if and only if you can split it into 1 or more subsequences such that each subsequence consists of consecutive integers and has length at least 3.
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1055 - Shortest Way To Form String
From any string, we can form a subsequence of that string by deleting some number of characters (possibly no deletions). Given two strings source and target, return the minimum number of subsequences of source such that their concatenation equals target. If the task is impossible, return -1.
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465 - Optimal Account Balancing
A group of friends went on holiday and sometimes lent each other money. For example, Alice paid for Bill’s lunch for $10. Then later Chris gave Alice $5 for a taxi ride. We can model each transaction as a tuple (x, y, z) which means person x gave person y $z. Assuming Alice, Bill, and Chris are person 0, 1, and 2 respectively (0, 1, 2 are the person’s ID), the transactions can be represented as [[0, 1, 10], [2, 0, 5]]. Given a list of transactions between a group of people, return the minimum number of transactions required to settle the debt.
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1000 - Minimum Cost To Merge Stones
There are N piles of stones arranged in a row. The i-th pile has stones[i] stones. A move consists of merging exactly K consecutive piles into one pile, and the cost of this move is equal to the total number of stones in these K piles. Find the minimum cost to merge all piles of stones into one pile. If it is impossible, return -1.
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809 - Expressive Words
Sometimes people repeat letters to represent extra feeling, such as “hello” -> “heeellooo”, “hi” -> “hiiii”. In these strings like “heeellooo”, we have groups of adjacent letters that are all the same: “h”, “eee”, “ll”, “ooo”. For some given string S, a query word is stretchy if it can be made to be equal to S by any number of applications of the following extension operation: choose a group consisting of characters c, and add some number of characters c to the group so that the size of the group is 3 or more.
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1110 - Delete Nodes And Return Forest
Given the root of a binary tree, each node in the tree has a distinct value. After deleting all nodes with a value in to_delete, we are left with a forest (a disjoint union of trees). Return the roots of the trees in the remaining forest. You may return the result in any order.
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1056 - Confusing Number
Given a number N, return true if and only if it is a confusing number, which satisfies the following condition: We can rotate digits by 180 degrees to form new digits. When 0, 1, 6, 8, 9 are rotated 180 degrees, they become 0, 1, 9, 8, 6 respectively. When 2, 3, 4, 5 and 7 are rotated 180 degrees, they become invalid. A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.
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1088 - Confusing Number II
We can rotate digits by 180 degrees to form new digits. When 0, 1, 6, 8, 9 are rotated 180 degrees, they become 0, 1, 9, 8, 6 respectively. When 2, 3, 4, 5 and 7 are rotated 180 degrees, they become invalid. A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.(Note that the rotated number can be greater than the original number.) Given a positive integer N, return the number of confusing numbers between 1 and N inclusive.
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1170 - Compare Strings By Frequency Of The Smallest Character
Let’s define a function f(s) over a non-empty string s, which calculates the frequency of the smallest character in s. For example, if s = “dcce” then f(s) = 2 because the smallest character is “c” and its frequency is 2. Now, given string arrays queries and words, return an integer array answer, where each answer[i] is the number of words such that f(queries[i]) < f(W), where W is a word in words.
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1155 - Number Of Dice Rolls With Target Sum
You have d dice, and each die has f faces numbered 1, 2, …, f. Return the number of possible ways (out of fd total ways) modulo 10^9 + 7 to roll the dice so the sum of the face up numbers equals target.
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545 - Boundary Of Binary Tree
Given a binary tree, return the values of its boundary in anti-clockwise direction starting from root. Boundary includes left boundary, leaves, and right boundary in order without duplicate nodes. (The values of the nodes may still be duplicates.)
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1152 - Analyze User Website Visit Pattern
We are given some website visits: the user with name username[i] visited the website website[i] at time timestamp[i]. A 3-sequence is a list of websites of length 3 sorted in ascending order by the time of their visits. (The websites in a 3-sequence are not necessarily distinct.) Find the 3-sequence visited by the largest number of users. If there is more than one solution, return the lexicographically smallest such 3-sequence.
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1099 - Two Sum Less Than K
Given an array A of integers and integer K, return the maximum S such that there exists i < j with A[i] + A[j] = S and S < K. If no i, j exist satisfying this equation, return -1.
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866 - Prime_Palindrome
Find the smallest prime palindrome greater than or equal to N.
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1102 - Path With Maximum Minimum Value
Given a matrix of integers A with R rows and C columns, find the maximum score of a path starting at [0,0] and ending at [R-1,C-1]. The score of a path is the minimum value in that path. For example, the value of the path 8 → 4 → 5 → 9 is 4. A path moves some number of times from one visited cell to any neighbouring unvisited cell in one of the 4 cardinal directions (north, east, west, south).
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694 - Number Of Distinct Islands
Given a non-empty 2D array grid of 0’s and 1’s, an island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. Count the number of distinct islands. An island is considered to be the same as another if and only if one island can be translated (and not rotated or reflected) to equal the other.
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819 - Most Common Word
Given a paragraph and a list of banned words, return the most frequent word that is not in the list of banned words. It is guaranteed there is at least one word that isn’t banned, and that the answer is unique. Words in the list of banned words are given in lowercase, and free of punctuation. Words in the paragraph are not case sensitive. The answer is in lowercase.
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1167 - Minimum Cost To Connect Sticks
You have some sticks with positive integer lengths. You can connect any two sticks of lengths X and Y into one stick by paying a cost of X + Y. You perform this action until there is one stick remaining. Return the minimum cost of connecting all the given sticks into one stick in this way.
