Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

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**Follow up:**Did you use extra space? A straight forward solution using O(m__n) space is probably a bad idea. A simple improvement uses O(m + n) space, but still not the best solution. Could you …

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Solve it without division and in O(n).

For example, given [1,2,3,4], return [24,12,8,6].

Follow up: Could you solve it with constant space complexity? (Note: …

Given a 2D board and a word, find if the word exists in the grid.

The word can be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same letter cell may not be used more than once.

思路：dfs即可。记得要回溯一下...

1/* …

Follow up for "Remove Duplicates": What if duplicates are allowed at most twice?

For example, Given sorted array nums = [1,1,1,2,2,3],

Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doesn't matter what you leave beyond the new length.

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Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).

Write a function to determine if a given target is in the array.

The array may contain duplicates.

好像阿里一面的时候问过。。。

思路：肯定是二分。。。不过由于有重复元素。。。所以很恶心。。。

According to the Wikipedia's article: "The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970."

Given a board with m by n cells, each cell has an initial state live (1) or dead (0). Each cell interacts with its eight neighbors …

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

For example, If nums = [1,2,2], a solution is:

[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

思路：

复习（？）一下 枚举子集的三种写法

（还有种更飘逸的...先不写了orz

这道题我用位向量法A的。。

/* ***********************************************

 1Author :111qqz
 2Created Time :2017年04月05日 星期三 16时49分57秒
 3File Name :106.cpp
 4************************************************ */
 5/**
 6 * Definition for a binary tree node.
 7 * struct TreeNode {
 8 *     int val;
 9 *     TreeNode *left;
10 *     TreeNode * …

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one.

Note:

  1. You **must not** modify the array (assume the array is read only).
  2. You must use …

Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array. Here a k-diff pair is defined as an integer pair (i, j), where i and j are both numbers in the array and their absolute difference is k.

Example 1:

1Input: [3, 1, 4, 1, 5], k = 2
2Output: 2
3Explanation: There …