细语呢喃

技术改变生活

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本次题解包括:

  • 389 Find the Difference
  • 390 Elimination Game
  • 391 Perfect Rectangle
  • 392 Is Subsequence
  • 393 UTF-8 Validation
  • 394 Decode String
  • 395 Longest Substring with At Least K Repeating Characters
  • 396 Rotate Function
  • 397 Integer Replacement
  • 398 Random Pick Index
  • 399 Evaluate Division
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Cool Idea

在UCAS进入研一的生活接近两个礼拜，发现老师的课件基本上都上传到课程网站，然后是一节一节给的。这样，每次老师更新课件的时候，我们都得开一下网页，然后看看是不是更新了？（虽然有邮箱提醒，但是这种邮件我都直接忽略的），于是萌生了写个脚本来自动下载的想法。

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leetcode Mini Parser

Given a nested list of integers represented as a string, implement a parser to deserialize it.

Each element is either an integer, or a list -- whose elements may also be integers or other lists.

Note: You may assume that the string is well-formed:

  • String is non-empty.
  • String does not contain white spaces.
  • String contains only digits 0-9, [, ,, ].

Example 1:

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Given s = "324",

You should return a NestedInteger object which contains a single integer 324.

Example 2:

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Given s = "[123,[456,[789]]]",

Return a NestedInteger object containing a nested list with 2 elements:

1. An integer containing value 123.
2. A nested list containing two elements:
    i.  An integer containing value 456.
    ii. A nested list with one element:
         a. An integer containing value 789.
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leetcode Shuffle an Array

Shuffle a set of numbers without duplicates.

Example:

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// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();


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leetcode Ransom Note

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.

Each letter in the magazine string can only be used once in your ransom note.

Note: You may assume that both strings contain only lowercase letters.

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canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true
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leetcode Insert Delete GetRandom O(1) - Duplicates allowed

Design a data structure that supports all following operations in average O(1) time.

Note: Duplicate elements are allowed.

  1. insert(val): Inserts an item val to the collection.
  2. remove(val): Removes an item val from the collection if present.
  3. getRandom: Returns a random element from current collection of elements. The probability of each element being returned is linearly related to the number of same value the collection contains.

Example:

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// Init an empty collection.
RandomizedCollection collection = new RandomizedCollection();

// Inserts 1 to the collection. Returns true as the collection did not contain 1.
collection.insert(1);

// Inserts another 1 to the collection. Returns false as the collection contained 1. Collection now contains [1,1].
collection.insert(1);

// Inserts 2 to the collection, returns true. Collection now contains [1,1,2].
collection.insert(2);

// getRandom should return 1 with the probability 2/3, and returns 2 with the probability 1/3.
collection.getRandom();

// Removes 1 from the collection, returns true. Collection now contains [1,2].
collection.remove(1);

// getRandom should return 1 and 2 both equally likely.
collection.getRandom();
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