概述 最近在写合约时遇到一些坑,做一下总结: 介绍主要分一下三个方面: 对区块链的简单描述 结合业务场景,编写简单智能合约,时遇到的坑(上篇) assembly 的使用说明(下篇) 正文 进入正题之前,我稍微简单介绍一下什么是区块链,区块链干嘛用的(特点),智能合约是做什么的,为什么要写只能合约(一下是个人理解仅供参考) 什么是区块链 A blockchain is a globally shared, transactional database. 译文:区块链是一个全局共享的事物数据库:(就…

当你开始学习使用solidity开发以太坊智能合约之后,很快你会碰到一个问题: 一.在solidity中该如何拼接字符串? 可能你已经试过了,下面的代码试图把两个字符串使用相加的运算符连接起来,但是这行不通: var str = 'asdf' var b = str + 'sdf' 实际上,根据solidity的官方文档,目前在solidity中,需要我们自己来实现字符串拼接功能. 二.拼接字符串实现代码 例如,下面的代码实现两个字符串的拼接,基本 上是利用bytes和string之间的类型转换…

如何将JSON文件存储在IPFS上,并使用Oraclize访问智能合约中的数据呢? 以太坊是一个成熟的区块链,使开发人员能够创建智能合约,在区块链上执行的程序可以由交易触发.人们经常将区块链称为数据库,但使用区块链作为数据存储非常昂贵. 以目前的价格(530美元,4gwei)在以太坊上存储250GB将花费你106,000,000美元.一般来说,我们可以忍受高成本因为我们: 不会在以太坊区块链上保存那么多数据. 区块链的审查制度,透明度和稳健性是值得的. 如果你是以太坊的新手,请查看此介绍. 去中…

# -*- coding: utf8 -*-'''__author__ = 'dabay.wang@gmail.com' 43: Multiply Stringshttps://leetcode.com/problems/multiply-strings/ Given two numbers represented as strings, return multiplication of the numbers as a string.Note: The numbers can be arbit…

March 18, 2016 Problem statement: https://www.hackerrank.com/challenges/two-strings/submissions/code/18506948 Julia likes to try a new way to train herself to expand C#/ C++ / Java / JavaScript languages, by reading the solutions, followed up with so…

StackOverFlow排错翻译 - Python字符串替换: How do I replace everything between two strings without replacing the strings? 原创连接: Python字符串替换 问题: Python:如何将两字符串之间的内容替换掉? I have this string(问题源码): str = ''' // DO NOT REPLACE ME // Anything might be here. Numbers…

Given two numbers represented as strings, return multiplication of the numbers as a string. Note: The numbers can be arbitrarily large and are non-negative. Converting the input string to integer is NOT allowed. You should NOT use internal library su…

Given two non-negative numbers num1 and num2 represented as string, return the sum of num1 and num2. Note: The length of both num1 and num2 is < 5100. Both num1 and num2 contains only digits 0-9. Both num1 and num2 does not contain any leading zero.…

Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings. Machine 1 (sender) has the function: string encode(vector<string> strs) { // ... your…

Given a string, we can "shift" each of its letter to its successive letter, for example: "abc" -> "bcd". We can keep "shifting" which forms the sequence: "abc" -> "bcd" -> ... -> &quo…