小结: 1.两个有限维度的向量空间,在同一数域下,是同构的 等价于 它们维数相等. Isomorphism 同构 0.1.8 Isomorphism. If U and V are vector spaces over the same scalar field F, and if f : U → V is an invertible function such that f (ax + by) = a f (x) + bf (y) for all x, y ∈ U and all a, b ∈…
Little Sub has a sequence . Now he has a problem for you. Two sequences of length and of length are considered isomorphic when they meet all the following two conditions: ; Define as the number of times integer occur in sequence . For each integer in…
I. 映射(Mapping) 1. 单射(Injective) 函数f 是单射当且仅当若f(x) = f(y) 则 x = y. 例子: f(x) = x+5 从实数集\(R\)到\(R\)是个单射函数. 这个函数很容易被还原:f(3) = 8,即 已知 8 可以返回 3 2. 满射(Surjective) 函数 f(从集 A 到集 B)是满射当且仅当在 B 中的每个 y 存在至少一个在 A 中的 x 满足 f(x) = y, 就是说, f 是满射当且仅当 f(A) = B. 值域里的每个元素都…
Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrences of a character must be replaced with another character while preserving the order of characters.…
React比较吸引我的地方在于其客户端-服务端同构特性,服务端-客户端可复用组件,本文来简单介绍下这一架构思想. 出于篇幅原因,本文不会介绍React基础,所以,如果你还不清楚React的state/props/生存周期等基本概念,建议先学习相关文档 客户端React 先来回顾一下React如何写一个组件.比如要做一个下面的表格: 可以这样写: 先创建一个表格类. Table.js var React = require('react'); var DOM = React.DOM; var ta…