向疯子致敬

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向那些疯狂的家伙们致敬，
他们特立独行，
他们桀骜不驯，
他们惹事生非，
他们格格不入，
他们用与众不同的眼光看待事物，
他们不喜欢墨守成规，
他们也不愿安于现状。
你可以引用他们，反对他们，
质疑他们，颂扬或是诋毁他们，
但唯独不能漠视他们。
因为他们改变了事物。
他们推动人类向前发展。
或许他们是别人眼里的疯子，
但他们却是我们眼中的天才。
因为只有那些疯狂到以为自己能够改变世界的人，
才能真正地改变世界。
——那些疯子就是我们
这两天回家了，无意中看到了微信BG的招聘软文，感觉写的很棒。
十年一梦，命运使然。最后去了SNG，算是完成了我儿时的梦想。

精准 优雅

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我从很小的时候就开始接触计算机了。

刚开始学习编程的时候，我惊叹于系统运作的分毫不差，总能带给我想要的结果。

后来进了校队，进了省队，去了无数大公司实习，设计了足够复杂的系统。计算机在我心中任然精准，但偶尔也会发现她缺了几斯灵性，少了几分优雅。之后又看到很多人说机器的冰冷无情，我不能理解，因为在我眼里计算机科学是一门精致的艺术，完美到丝毫不差。

直到再后来，我经历了世事，才发现其实机器的精准优雅一成不变，只是我们触到了他冰冷的心。

Excel Sheet Column Title

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Given a positive integer, return its corresponding column title as appear in an Excel sheet.
For example:

    1 -> A
    2 -> B
    3 -> C
    ...
    26 -> Z
    27 -> AA
    28 -> AB

这题看起来不难，但居然做了我两个小时。其中还是有很多值得注意一下的地方的。

def convertToTitle2(n):
    ret = ""
    while(n):
        ret = chr( (n-1)%26 + 65 ) + ret
        n = (n-1)/26 #核心
    return ret

先贴一下最后AC的代码。我之前用了很长的代码去判断字符进位的情况，但效果都不理想。

Power of Three

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Given an integer, write a function to determine if it is a power of three.

class Solution(object):
    def isPowerOfThree(self, n):
        #while (n and (n % 3 == 0)):
            #n = n / 3
        #return n == 1
        
        
        #return (n > 0 and 1162261467 % n == 0)
        
        return (n > 0 and int(math.log10(n) / math.log10(3)) - math.log10(n) / math.log10(3) == 0)

Maximum Depth of Binary Tree

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Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root)
    {
        if(root == NULL)
            return 0;  
        int res = 1;  
        int l = maxDepth(root->left);  
        int r = maxDepth(root->right);  
        return l > r? l + 1:r+ 1;  
    }
};

Contains Duplicate

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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 array, and it should return false if every element is distinct.

class Solution {
public:
    bool containsDuplicate(vector<int>& nums)
    {
        if(nums.empty())
            return false;
            
        set<int> s;
        vector<int>::iterator itr = nums.begin();
        
        while(itr != nums.end())
        {
            if(s.count(*itr) == 1)
                return true;
            s.insert(*itr);
            itr++;
        }
        return false;
    }
};

Power of two

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Given an integer, write a function to determine if it is a power of two.

class Solution(object):
    def isPowerOfTwo(self, n):
        while (n and (n % 2 == 0)):
            n = n / 2
            
        return n == 1
        
        #Certainly,you can also use the following method
        #return (n and (n&(n-1))) == 0

Ugly number

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Write a program to check whether a given number is an ugly number.
Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.
Note that 1 is typically treated as an ugly number.

class Solution(object):
    def isUgly(self, number):
        if number == 1:
            return True
        if number == 0:
            return False
        
        while(number % 2 == 0):
            number /= 2
        while(number % 3 == 0):
            number /= 3
        while(number % 5 == 0):
            number /= 5
    
        return number == 1