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Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. For example,If n = 4 and k = 2, a solution is: [ [2,4], [3,4 阅读全文
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Suppose you have N integers from 1 to N. We define a beautiful arrangement as an array that is constructed by these N numbers successfully if one of t 阅读全文
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A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element. Now given an M x N matrix, return True if and only if the m 阅读全文
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A sequence of number is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the 阅读全文
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Given a list of positive integers, the adjacent integers will perform the float division. For example, [2,3,4] -> 2 / 3 / 4. However, you can add any 阅读全文
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You need to find the largest value in each row of a binary tree. Example: Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9] You need to find the largest 阅读全文
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Given a string, your task is to count how many palindromic substrings in this string. The substrings with different start indexes or end indexes are c 阅读全文
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Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element 阅读全文
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Given a binary tree, find the leftmost value in the last row of the tree. Example 1: Example 2: Note: You may assume the tree (i.e., the given root no 阅读全文
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Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twi 阅读全文