read/writeNotes

Posted on 2020-10-12

写好笔记不是一件容易的事情

想想距离上一篇笔记. 我已经咕了一个月了.

已经渐渐丧失当初写笔记的热情了… 期间也看了很多其他人写的笔记(有些写得真的好👌). 也越发体会到要写好. 写得至少之后自己能看懂. 写全面. 是很不容易的一件事情. 首先你得需要对笔记中的东西知根知底. 其次要组织语言. 排版. 最好应用表格和动态图片解释. …

但是! 在下并不是说自己不写了!

只是. emm… 吐槽一下…

言归正传, 今天带来的对于 diffie-hellman key exchange 算法的讨论(那是真的头疼 = =)

read/SICP

Posted on 2020-09-09

“I think that it’s extraordinarily important that we in computer science keep fun in computing. When it started out, it was an awful lot of fun. Of course, the paying customers got shared every now and then, and after a while we began to take their complaints seriously. We began to feel as if we really were responsible for the successful, error-free perfect use of these machines. I don’t think we are. I think we’re responsible for stretching them, setting them off in new directions, and keeping fun in the house. I hope the field of computer science never loses its sense of fun. Above all, I hope we don’t become missionaries. Don’t feel as if you’re Bible salesmen. The world has too many of those already. What you know about computing other people will learn. Don’t feel as if the key to successful computing is only in your hands. What’s in your hands, I think and hope, is intelligence: the ability to see the machine as more than when you were first led up to it, that you can make it more.”

感觉受到了莫大的鼓舞. 尤其是 What’s in your hands, I think and hope, is intelligence: the ability to see the machine as more than when you were first led up to it, that you can make it more.”

PS: 现在正在读 “structure and interpretation of computer programs” . 以上是这本书的前言. 这本书应该是第三次读了. 这次我要认真读完! :)

read/C++14C++17

Posted on 2020-09-06

C++14~C++17

之前我总结过 C++14 的一些东西, 但现在已经 2020 了啊 = =

所以就想着… emm… 虽然项目还是在用 C11 的东西, 连 C14 都没有. 但是! 需求不会留给你学习的时间的!(即使有, 但那对我不成立!) 所以就再看看 C17 的吧(虽然 C20 已经有了, 不过离实现和稳定还有一段时间, 有其他更优先的事情) 顺便对 C14 回顾一下 :happy:

(PS: 这次在下选择了 cppreference 作为参考)

leetcode/PartitionArrayintoDisjointintervals

Posted on 2020-09-02

Partition Array into Disjoint intervals

我的思维好像固定了 = =…

read/PartitionArrayintoDisjointintervals

Posted on 2020-09-02

Partition Array into Disjoint intervals

我的思维好像固定了 = =…

my solution

class Solution {
public:
    int partitionDisjoint(vector<int>& A) {
        int b = 0, e = A.size() - 1;
        int lx = A[b];
        while (b < e) {
            while (e > b && A[e] >= lx) { --e; }
            // A[e] will less than lx
            
            int olx = lx;
            while (b < e) {
                lx = max(lx, A[++b]);
            }
            // lx is max[A[0] - A[e]]
            
            if (olx != lx) {
                // recalculate
                e = A.size() - 1;
            }
        }
        
        return b + 1;
    }
};

lx 是左边已遍历最大值. e 在每次遍历后将会指向一个从右往左第一个小于这个值的下标.

b 的迭代不会重复, 而 e 的迭代是可能重复的, 这是这个解法的瓶颈.

other solution

PS: 以后没有 the best solution 了. 因为很难说一个算法是 best 的. 因为实际的输入不定. 适用于输入的算法也不定. 并且提交里面往往并不是最好的算法. Discuss 里面才有.

参照

class Solution {
public:
    int partitionDisjoint(vector<int>& A) {
        int b = 0, e = 0;
        int lx = A[b], rlx = lx;
        for (int i = 0; i < A.size(); ++i) {
            if (A[i] < lx) {
                e = i;
                lx = rlx;
            } else if (A[i] > rlx) {
                rlx = A[i];
            }
        }
        
        //printf("rlx: %d, lx: %d", rlx, lx);
        return e + 1;
    }
};