Given two strings s and t, determine if they are isomorphic.
Two strings s and t are isomorphic if the characters in s can be replaced to get t.
All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.
There is an exam room with n seats in a single row labeled from 0 to n - 1.
When a student enters the room, they must sit in the seat that maximizes the distance to the closest person. If there are multiple such seats, they sit in the seat with the lowest number. If no one is in the room, then the student sits at seat number 0.
Design a class that simulates the mentioned exam room.
Implement the ExamRoom class:
- ExamRoom(int n) Initializes the object of the exam room with the number of the seats n.
- int seat() Returns the label of the seat at which the next student will set.
- void leave(int p) Indicates that the student sitting at seat p will leave the room. It is guaranteed that there will be a student sitting at seat p.
We can represent a sentence as an array of words, for example, the sentence “I am happy with leetcode” can be represented as arr = [“I”,”am”,happy”,”with”,”leetcode”].
Given two sentences sentence1 and sentence2 each represented as a string array and given an array of string pairs similarPairs where similarPairs[i] = [xi, yi] indicates that the two words xi and yi are similar.
Return true if sentence1 and sentence2 are similar, or false if they are not similar.
Two sentences are similar if:
- They have the same length (i.e., the same number of words)
- sentence1[i] and sentence2[i] are similar.
Notice that a word is always similar to itself, also notice that the similarity relation is not transitive. For example, if the words a and b are similar, and the words b and c are similar, a and c are not necessarily similar.
We can represent a sentence as an array of words, for example, the sentence “I am happy with leetcode” can be represented as arr = [“I”,”am”,happy”,”with”,”leetcode”].
Given two sentences sentence1 and sentence2 each represented as a string array and given an array of string pairs similarPairs where similarPairs[i] = [xi, yi] indicates that the two words xi and yi are similar.
Return true if sentence1 and sentence2 are similar, or false if they are not similar.
Two sentences are similar if:
- They have the same length (i.e., the same number of words)
- sentence1[i] and sentence2[i] are similar.
Notice that a word is always similar to itself, also notice that the similarity relation is transitive. For example, if the words a and b are similar, and the words b and c are similar, then a and c are similar.
Android devices have a special lock screen with a 3 x 3 grid of dots. Users can set an “unlock pattern” by connecting the dots in a specific sequence, forming a series of joined line segments where each segment’s endpoints are two consecutive dots in the sequence. A sequence of k dots is a valid unlock pattern if both of the following are true:
- All the dots in the sequence are distinct.
- If the line segment connecting two consecutive dots in the sequence passes through the center of any other dot, the other dot must have previously appeared in the sequence. No jumps through the center non-selected dots are allowed.
- For example, connecting dots 2 and 9 without dots 5 or 6 appearing beforehand is valid because the line from dot 2 to dot 9 does not pass through the center of either dot 5 or 6.
- However, connecting dots 1 and 3 without dot 2 appearing beforehand is invalid because the line from dot 1 to dot 3 passes through the center of dot 2.
Here are some example valid and invalid unlock patterns:
- The 1st pattern [4,1,3,6] is invalid because the line connecting dots 1 and 3 pass through dot 2, but dot 2 did not previously appear in the sequence.
- The 2nd pattern [4,1,9,2] is invalid because the line connecting dots 1 and 9 pass through dot 5, but dot 5 did not previously appear in the sequence.
- The 3rd pattern [2,4,1,3,6] is valid because it follows the conditions. The line connecting dots 1 and 3 meets the condition because dot 2 previously appeared in the sequence.
- The 4th pattern [6,5,4,1,9,2] is valid because it follows the conditions. The line connecting dots 1 and 9 meets the condition because dot 5 previously appeared in the sequence.
Given two integers m and n, return the number of unique and valid unlock patterns of the Android grid lock screen that consist of at least m keys and at most n keys.
Two unlock patterns are considered unique if there is a dot in one sequence that is not in the other, or the order of the dots is different.
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.
You are given an array of points in the X-Y plane points where points[i] = [xi, yi].
Return the minimum area of a rectangle formed from these points, with sides parallel to the X and Y axes. If there is not any such rectangle, return 0.
Given two vectors of integers v1 and v2, implement an iterator to return their elements alternately.
Implement the ZigzagIterator class:
- ZigzagIterator(List
v1, List v2) initializes the object with the two vectors v1 and v2. - boolean hasNext() returns true if the iterator still has elements, and false otherwise.
- int next() returns the current element of the iterator and moves the iterator to the next element.
1444. Number of Ways of Cutting a Pizza
Given a rectangular pizza represented as a rows x cols matrix containing the following characters: ‘A’ (an apple) and ‘.’ (empty cell) and given the integer k. You have to cut the pizza into k pieces using k-1 cuts.
For each cut you choose the direction: vertical or horizontal, then you choose a cut position at the cell boundary and cut the pizza into two pieces. If you cut the pizza vertically, give the left part of the pizza to a person. If you cut the pizza horizontally, give the upper part of the pizza to a person. Give the last piece of pizza to the last person.
Return the number of ways of cutting the pizza such that each piece contains at least one apple. Since the answer can be a huge number, return this modulo 10^9 + 7.
428. Serialize and Deserialize N-ary Tree
Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.
Design an algorithm to serialize and deserialize an N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that an N-ary tree can be serialized to a string and this string can be deserialized to the original tree structure.
For example, you may serialize the following 3-ary tree
as [1 [3[5 6] 2 4]]. Note that this is just an example, you do not necessarily need to follow this format.Or you can follow LeetCode’s level order traversal serialization format, where each group of children is separated by the null value.
For example, the above tree may be serialized as [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14].You do not necessarily need to follow the above-suggested formats, there are many more different formats that work so please be creative and come up with different approaches yourself.
