随笔分类 - Leetcode
摘要：Given a string S that only contains "I" (increase) or "D" (decrease), let N = S.length. Return any permutation A of [0, 1, ..., N] such that for all i
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摘要：Preorder: Approach #1: Recurisive. Approach #2: Iteratively.[Java] Approach #3: Morris Traversal.[C++] Using Morris Traversal can don't use recurisive
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摘要：We are given an array A of N lowercase letter strings, all of the same length. Now, we may choose any set of deletion indices, and for each string, we
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摘要：Given an array A of integers, return true if and only if it is a valid mountain array. Recall that A is a mountain array if and only if: A.length >= 3
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摘要：Sometimes people repeat letters to represent extra feeling, such as "hello" -> "heeellooo", "hi" -> "hiiii". Here, we have groups, of adjacent letters
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摘要：A website domain like "discuss.leetcode.com" consists of various subdomains. At the top level, we have "com", at the next level, we have "leetcode.com
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摘要：Given a string, sort it in decreasing order based on the frequency of characters. Example 1: Example 2: Example 3: Approach #1: c++.
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摘要：Given n points in the plane that are all pairwise distinct, a "boomerang" is a tuple of points (i, j, k) such that the distance between i and j equals
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摘要：Given a string s and a non-empty string p, find all the start indices of p's anagrams in s. Strings consists of lowercase English letters only and the
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摘要：Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters. This
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摘要：Given two strings s and t which consist of only lowercase letters. String t is generated by random shuffling string s and then add one more letter at
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摘要：Design a data structure that supports all following operations in average O(1) time. Note: Duplicate elements are allowed. Example: Approach #1: C++.
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摘要：Design a data structure that supports all following operations in average O(1) time. insert(val): Inserts an item val to the set if not already presen
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摘要：Design a simplified version of Twitter where users can post tweets, follow/unfollow another user and is able to see the 10 most recent tweets in the u
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摘要：Given a non-empty array of integers, return the k most frequent elements. Example 1: Input: nums = [1,1,1,2,2,3], k = 2 Output: [1,2] Example 2: Input
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摘要：Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the arr
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摘要：Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the
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摘要：Given a non-empty array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runti
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摘要：A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null. Return a deep copy
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摘要：Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive intege
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