LC. 4052. Cyclically Shift Rows and Columns
Solved
Easy
Hint
You are given an integer n, a 2D integer array grid of size n x n, and two integer arrays rowShift and colShift, each of length n, where:
rowShift[i] represents the number of positions to cyclically shift the ith row of grid to the left.
colShift[j] represents the number of positions to cyclically shift the jth column of grid upward.
First, cyclically shift each row according to rowShift, then cyclically shift each column of the resulting grid according to colShift.
Return the resulting grid after performing all the shifts.
A cyclic left shift of a row by k positions moves the element at column j to column (j - k + n) % n. All other rows remain unchanged.
A cyclic upward shift of a column by k positions moves the element at row i to row (i - k + n) % n. All other columns remain unchanged.
LC. 4048. Count Values With Equally Spaced Occurrences I
You are given an integer array nums.
An integer x is called special if:
x appears exactly three times in nums.
All three occurrences of x are equally spaced in nums. In other words, if all occurrences of x are at indices i1 < i2 < i3, then i2 - i1 = i3 - i2.
Return the number of distinct special integers in nums.
Example 1:
Input: nums = [1,8,1,5,1,5,8,5]
Output: 2
Explanation:
1 is special because it occurs exactly three times at equally spaced indices 0, 2, and 4.
5 is special because it occurs exactly three times at equally spaced indices 3, 5, and 7.
8 is not special because it occurs only twice.
Therefore, the answer is 2.
Example 2:
Input: nums = [8,8,8,8]
Output: 0
Explanation:
8 is not special because it does not occur exactly three times. Therefore, the answer is 0.
Example 3:
Input: nums = [8,6,6,8,8]
Output: 0
Explanation:
8 occurs at indices 0, 3, and 4, which are not equally spaced. 6 occurs only twice. Therefore, no integer is special.
LC. 4049. Count Values With Equally Spaced Occurrences II
You are given an integer array nums.
An integer x is called special if:
x appears at least three times in nums.
All occurrences of x are equally spaced in nums. In other words, if all occurrences of x are at indices i1 < i2 < ... < im, then i2 - i1 = i3 - i2 = ... = im - im-1.
Return the number of distinct special integers in nums.
Example 1:
Input: nums = [1,8,1,5,1,5,8,5]
Output: 2
Explanation:
1 is special because it occurs at equally spaced indices 0, 2, and 4.
5 is special because it occurs at equally spaced indices 3, 5, and 7.
8 is not special because it occurs only twice.
Therefore, the answer is 2.
Example 2:
Input: nums = [8,8,8,8]
Output: 1
Explanation:
8 is special because it occurs at equally spaced indices 0, 1, 2, and 3. Therefore, the answer is 1.
Example 3:
Input: nums = [8,6,6,8,8]
Output: 0
Explanation:
8 occurs at indices 0, 3, and 4, which are not equally spaced. 6 occurs only twice. Therefore, no integer is special.
Given a 0-indexed integer array nums of length n and an integer target, return the number of pairs (i, j) where 0 <= i < j < n and nums[i] + nums[j] < target.
Example 1:
Input: nums = [-1,1,2,3,1], target = 2
Output: 3
Explanation: There are 3 pairs of indices that satisfy the conditions in the statement:
- (0, 1) since 0 < 1 and nums[0] + nums[1] = 0 < target
- (0, 2) since 0 < 2 and nums[0] + nums[2] = 1 < target
- (0, 4) since 0 < 4 and nums[0] + nums[4] = 0 < target
Note that (0, 3) is not counted since nums[0] + nums[3] is not strictly less than the target.
Example 2:
Input: nums = [-6,2,5,-2,-7,-1,3], target = -2
Output: 10
Explanation: There are 10 pairs of indices that satisfy the conditions in the statement:
- (0, 1) since 0 < 1 and nums[0] + nums[1] = -4 < target
- (0, 3) since 0 < 3 and nums[0] + nums[3] = -8 < target
- (0, 4) since 0 < 4 and nums[0] + nums[4] = -13 < target
- (0, 5) since 0 < 5 and nums[0] + nums[5] = -7 < target
- (0, 6) since 0 < 6 and nums[0] + nums[6] = -3 < target
- (1, 4) since 1 < 4 and nums[1] + nums[4] = -5 < target
- (3, 4) since 3 < 4 and nums[3] + nums[4] = -9 < target
- (3, 5) since 3 < 5 and nums[3] + nums[5] = -3 < target
- (4, 5) since 4 < 5 and nums[4] + nums[5] = -8 < target
- (4, 6) since 4 < 6 and nums[4] + nums[6] = -4 < target
如果 nums[left] + nums[right] < target：
因为数组已经排序，nums[right] 是当前能取到的最大值。如果最小值和当前最大值的和都小于 target，那么 nums[left] 和 left 到 right 之间的任何一个数相加，必定也都小于 target。
所以，包含 nums[left] 的有效对数直接就是 right - left 个。统计完之后，让 left 向右移动一位（left++）。
2825. Make String a Subsequence Using Cyclic Increments
You are given two 0-indexed strings str1 and str2.
In an operation, you select a set of indices in str1, and for each index i in the set, increment str1[i] to the next character cyclically. That is 'a' becomes 'b', 'b' becomes 'c', and so on, and 'z' becomes 'a'.
Return true if it is possible to make str2 a subsequence of str1 by performing the operation at most once, and false otherwise.
Note: A subsequence of a string is a new string that is formed from the original string by deleting some (possibly none) of the characters without disturbing the relative positions of the remaining characters.
Example 1:
Input: str1 = "abc", str2 = "ad"
Output: true
Explanation: Select index 2 in str1.
Increment str1[2] to become 'd'.
Hence, str1 becomes "abd" and str2 is now a subsequence. Therefore, true is returned.
Example 2:
Input: str1 = "zc", str2 = "ad"
Output: true
Explanation: Select indices 0 and 1 in str1.
Increment str1[0] to become 'a'.
Increment str1[1] to become 'd'.
Hence, str1 becomes "ad" and str2 is now a subsequence. Therefore, true is returned.
Example 3:
Input: str1 = "ab", str2 = "d"
Output: false
Explanation: In this example, it can be shown that it is impossible to make str2 a subsequence of str1 using the operation at most once.
Therefore, false is returned.
Constraints:
1 <= str1.length <= 105
1 <= str2.length <= 105
str1 and str2 consist of only lowercase English letters.
2619. Array Prototype Last
Easy
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Hint
Write code that enhances all arrays such that you can call the array.last() method on any array and it will return the last element. If there are no elements in the array, it should return -1.
You may assume the array is the output of JSON.parse.
Example 1:
Input: nums = [null, {}, 3]
Output: 3
Explanation: Calling nums.last() should return the last element: 3.
Example 2:
Input: nums = []
Output: -1
Explanation: Because there are no elements, return -1.
2618. Check if Object Instance of Class
Medium
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Hint
Write a function that checks if a given value is an instance of a given class or superclass. For this problem, an object is considered an instance of a given class if that object has access to that class's methods.
There are no constraints on the data types that can be passed to the function. For example, the value or the class could be undefined.
Example 1:
Input: func = () => checkIfInstanceOf(new Date(), Date)
Output: true
Explanation: The object returned by the Date constructor is, by definition, an instance of Date.
Example 2:
Input: func = () => { class Animal {}; class Dog extends Animal {}; return checkIfInstanceOf(new Dog(), Animal); }
Output: true
Explanation:
class Animal {};
class Dog extends Animal {};
checkIfInstanceOf(new Dog(), Animal); // true
Dog is a subclass of Animal. Therefore, a Dog object is an instance of both Dog and Animal.
Example 3:
Input: func = () => checkIfInstanceOf(Date, Date)
Output: false
Explanation: A date constructor cannot logically be an instance of itself.
Example 4:
Input: func = () => checkIfInstanceOf(5, Number)
Output: true
Explanation: 5 is a Number. Note that the "instanceof" keyword would return false. However, it is still considered an instance of Number because it accesses the Number methods. For example "toFixed()".
2774. Array Upper Bound
Easy
Hint
Write code that enhances all arrays such that you can call the upperBound() method on any array and it will return the last index of a given target number. nums is a sorted ascending array of numbers that may contain duplicates. If the target number is not found in the array, return -1.
Example 1:
Input: nums = [3,4,5], target = 5
Output: 2
Explanation: Last index of target value is 2
Example 2:
Input: nums = [1,4,5], target = 2
Output: -1
Explanation: Because there is no digit 2 in the array, return -1.
Example 3:
Input: nums = [3,4,6,6,6,6,7], target = 6
Output: 5
Explanation: Last index of target value is 5
Constraints:
1 <= nums.length <= 104
-104 <= nums[i], target <= 104
nums is sorted in ascending order.
Follow up: Can you write an algorithm with O(log n) runtime complexity?
interface Array<T> {
upperBound(target: number): number;
}
Array.prototype.upperBound = function(target: number): number {
2775. Undefined to Null
Medium
Given a deeply nested object or array obj, return the object obj with any undefined values replaced by null.
undefined values are handled differently than null values when objects are converted to a JSON string using JSON.stringify(). This function helps ensure serialized data is free of unexpected errors.
Example 1:
Input: obj = {"a": undefined, "b": 3}
Output: {"a": null, "b": 3}
Explanation: The value for obj.a has been changed from undefined to null
Example 2:
Input: obj = {"a": undefined, "b": ["a", undefined]}
Output: {"a": null,"b": ["a", null]}
Explanation: The values for obj.a and obj.b[1] have been changed from undefined to null
Constraints:
obj is a valid JSON object or array
2 <= JSON.stringify(obj).length <= 105
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