100 numpy exercises

This is a collection of exercises that have been collected in the numpy mailing list, on stack
overflow
and in the numpy documentation. The goal of this collection is to offer a quick reference for both old
and new
users but also to provide a set of exercises for those who teach.

If you find an error or think you’ve a better way to
solve some of them, feel
free to open an issue at https://github.com/rougier/numpy-100.
File automatically generated. See the documentation to update questions/answers/hints programmatically.

哈夫曼树类，实现了哈夫曼树的构造和哈夫曼编码的功能

趁着线性代数的知识还热乎，简短的写了个矩阵类的demo，目前实现了

• 矩阵的构造
• 矩阵的运算(+ - * =)
• 矩阵的读写

需不断更新…（对角矩阵、求矩阵的逆、伴随矩阵、对称矩阵、特征值与特征向量、矩阵相似判断、是否可对角化、二次型等实际需要时再继续学习)

At the film’s beginning, Hank (Paul Dano) prepares to commit suicide on a deserted island, and suddenly a corpse is washed ashore by the waves. Interestingly, this corpse is farting every second, which disturbs Hank’s suicide. Hence Hank goes ahead and has a look. Then Hank stops killing himself, dragging the dead man named Manny by Hank, into a cave. It is so funny that Harry Porter’s actor, Daniel Radcliffe, portrays the never-stop-farted corpse so that reports tell the story bluntly: Daniel Radcliffe farts a lot in this movie.

求next数组

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int* getNext(string str) {
	int str_len = str.size();
	int* next = new int[str_len];//为申请next数组申请内存空间
	next[0] = 0;
	next[1] = 0;
	int prefix = 0;
	int index = 2;
	//比较前缀与后缀
	while(index<str_len) {
		if (str[index-1] == str[prefix]) {
			prefix++;
			next[index] = prefix;
			index++;
		}
		else {
			if (prefix == 0) {
				next[index] = prefix;
				index++;
			}
			else
				prefix = next[prefix-1];
		}
	}
	return next;
}

kmp算法

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int KMP(string pattern, string str) {
	//得到next数组
	int* next = getNext(pattern);
	int i = 0, j = 0;//两个索引分别代表主串和模式串的下标
	//主串与模式进行比较
	while (i < str.size()) {
		//字符匹配则主串模式串索引均后移
		if (str[i] == pattern[j]||j==0) {
			i++;j++;
			if (j >= pattern.size()) {
				break;
			}
		}
		//不匹配，主串索引不变，模式串索引根据next数组作相应的改变
		else {

			j = next[j];
		}
	}
	delete [] next;
	if (j == pattern.size())
		return i - pattern.size();
	else return -1;
}

本文用C++阐述十大排序算法的升降序实现方法。

• 交换排序（冒泡，快排）
• 插入排序（简单插入，希尔）
• 选择排序、堆排序
• 归并排序
• 基数排序，计数排序，桶排序

本文从五个方面详述C++11特性：

• 关键字与变量的使用
• 面向对象特性(委托构造函数，继承构造函数，可调用对象包装器、邦定器，lambda表达式等)
• 移动语义
• 智能指针
• 多线程

本文讲述树的遍历各种操作，层次遍历，前中后三种次序的遍历的迭代实现方式。其中包含力扣的相关题目。

开篇之前，先通过先序遍历的次序构建二叉树。(本片代码以二叉树为主，故多叉树结构暂不编写)

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//二叉树结构体
struct BiTree {
	char val;
	BiTree* left=NULL;
	BiTree* right=NULL;
};
//先序创建二叉树
void createTree(BiTree* &root) {
	char ch;
	cin >> ch;
	if (ch != 'x') {//x表示为空结点
		root = new BiTree;
		root->val = ch;
		createTree(root->left);
		createTree(root->right);

	}
	else root = NULL;
}

本文记录学习0-1背包问题时的总结，详细介绍了对背包问题的暴力解法，二维数组的思路以及滚动数组思路的理解，并给出详细注释与代码。

定时任务调度

• crontab 定时任务设置

​ -e 编辑crontab定时任务

​ -l 查询crontab任务

​ -r 删除当前用户所有的crontab任务