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部分章节是看文章和视频的，自行查看哈，这里从实际操作开始。

Keeping Track of Blockchain User State

Coding the UTXO Model

1: Transaction Output

查看要求：

输入：

class TXO {
    constructor(owner, amount) {
        this.owner = owner;
        this.amount = amount;
        this.spent = false;
    }
    spend() {
        this.spent = true;
    }
}

module.exports = TXO;

点击运行。

2: Spent TXOs\ 查看要求：

输入：

class Transaction {
    constructor(inputUTXOs, outputUTXOs) {
        this.inputUTXOs = inputUTXOs;
        this.outputUTXOs = outputUTXOs;
    }
    execute() {
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            if (this.inputUTXOs[i].spent) {
                throw new Error("already spent");
            }
        }
    }
}

module.exports = Transaction;

点击运行。

3: Sufficient Amount

查看要求：

class Transaction {
    constructor(inputUTXOs, outputUTXOs) {
        this.inputUTXOs = inputUTXOs;
        this.outputUTXOs = outputUTXOs;
    }
    execute() {
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            if (this.inputUTXOs[i].spent) {
                throw new Error("already spent");
            }
        }

        let inn = 0;
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            inn = inn + this.inputUTXOs[i].amount;
        }
        let out = 0;
        for (let i = 0; i < this.outputUTXOs.length; i++) {
            out = out + this.outputUTXOs[i].amount;
        }
        if (inn < out) {
            throw new Error("less than");
        }
    }
}

module.exports = Transaction;

点击运行。

4: Successful Execute

查看要求：

输入：

class Transaction {
    constructor(inputUTXOs, outputUTXOs) {
        this.inputUTXOs = inputUTXOs;
        this.outputUTXOs = outputUTXOs;
    }
    execute() {
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            if (this.inputUTXOs[i].spent) {
                throw new Error("already spent");
            }
        }

        let inn = 0;
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            inn = inn + this.inputUTXOs[i].amount;
        }
        let out = 0;
        for (let i = 0; i < this.outputUTXOs.length; i++) {
            out = out + this.outputUTXOs[i].amount;
        }
        if (inn < out) {
            throw new Error("less than");
        }

        for (let i = 0; i < this.inputUTXOs.length; i++) {
            this.inputUTXOs[i].spend();
        }
    }
}

module.exports = Transaction;

点击运行。

5: Miner's Fee

查看要求：

输入：

class Transaction {
    constructor(inputUTXOs, outputUTXOs) {
        this.inputUTXOs = inputUTXOs;
        this.outputUTXOs = outputUTXOs;
    }
    execute() {
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            if (this.inputUTXOs[i].spent) {
                throw new Error("already spent");
            }
        }

        let inn = 0;
        for (let i = 0; i < this.inputUTXOs.length; i++) {
            inn = inn + this.inputUTXOs[i].amount;
        }
        let out = 0;
        for (let i = 0; i < this.outputUTXOs.length; i++) {
            out = out + this.outputUTXOs[i].amount;
        }
        if (inn < out) {
            throw new Error("less than");
        }

        for (let i = 0; i < this.inputUTXOs.length; i++) {
            this.inputUTXOs[i].spend();
        }

        this.fee = inn - out;
    }
}

module.exports = Transaction;

点击运行。

Tree Data Structures

Build a Binary Search Tree

1: Node

查看要求：

输入：

class Node {
    constructor(data) {
        this.data = data;
        this.left = null;
        this.right = null;
    }
}

module.exports = Node;

点击运行。

2: Tree

查看要求：

输入：

class Tree {
    constructor() {
        this.root = null;
    }
}

module.exports = Tree;

点击运行。

3: Add Root

查看要求：

输入：

class Tree {
    constructor() {
        this.root = null;
    }

    addNode(node) {
        this.root = node;
    }
}

module.exports = Tree;

点击运行。

4: First Layer

查看要求：

输入：

class Tree {
    constructor() {
        this.root = null;
    }

    addNode(node) {
        if (this.root === null) {
            this.root = node;
        } else if (this.root.data > node.data) {
            this.root.left = node;
        } else {
            this.root.right = node;
        }
    }
}

module.exports = Tree;

点击运行。

5: Many Layers

查看要求：

输入：

class Tree {
    constructor() {
        this.root = null;
    }

    addNode(node) {
        if (this.root === null) {
            this.root = node;
        } else {
            let p = this.root;
            while (true) {
                if (p.data > node.data) {
                    if (p.left) {
                        p = p.left;
                    } else {
                        p.left = node;
                        break;
                    }
                } else {
                    if (p.right) {
                        p = p.right;
                    } else {
                        p.right = node;
                        break;
                    }
                }
            }
        }
    }
}

module.exports = Tree;

点击运行。

6: Search

查看要求：

输入：

class Tree {
    constructor() {
        this.root = null;
    }

    addNode(node) {
        if (this.root === null) {
            this.root = node;
        } else {
            let p = this.root;
            while (true) {
                if (p.data > node.data) {
                    if (p.left) {
                        p = p.left;
                    } else {
                        p.left = node;
                        break;
                    }
                } else {
                    if (p.right) {
                        p = p.right;
                    } else {
                        p.right = node;
                        break;
                    }
                }
            }
        }
    }

    hasNode(number) {
        let n = this.root;
        while(n) {
            if (n.data === number) {
                return true;
            } else {
                if (n.data > number) {
                    n = n.left;
                } else {
                    n = n.right;
                }
            }
        }
        return false;
    }
}

module.exports = Tree;

点击运行。

Merkle Trees

1: Combine Two Leaves

查看要求：

输入：

class MerkleTree {
    constructor(leaves, concat) {
        this.leaves = leaves;
        this.concat = concat;
    }
    getRoot() {
        return this.concat(this.leaves[0], this.leaves[1]);
    }
}

module.exports = MerkleTree;

点击运行。

2: Multiple Layers

查看要求：

输入：

class MerkleTree {
    constructor(leaves, concat) {
        this.leaves = leaves;
        this.concat = concat;
    }
    getRoot(next = this.leaves) {
        while(true) {
            if (next.length <= 1) {
                return next;
            }
            let level = [];
            for (let i = 0; i < next.length; i+=2) {
                level.push(this.concat(next[i], next[i+1]));
            }
            next = level;
        }
    }
}

module.exports = MerkleTree;

点击运行。

3: Odd Leaves

查看要求：

输入：

class MerkleTree {
    constructor(leaves, concat) {
        this.leaves = leaves;
        this.concat = concat;
    }
    getRoot(next = this.leaves) {
        while (true) {
            if (next.length <= 1) {
                return next;
            }
            let level = [];
            for (let i = 0; i < next.length; i += 2) {
                if ((i + 1) >= next.length) {
                    level.push(next[i]);
                } else {
                    level.push(this.concat(next[i], next[i + 1]));
                }
            }
            next = level;
        }
    }
}

module.exports = MerkleTree;

点击运行。

4: Build the Proof

查看要求：

输入：

class MerkleTree {
    constructor(leaves, concat) {
        this.leaves = leaves;
        this.concat = concat;
    }
    getRoot(next = this.leaves) {
        while (true) {
            if (next.length <= 1) {
                return next;
            }
            let level = [];
            for (let i = 0; i < next.length; i += 2) {
                if ((i + 1) >= next.length) {
                    level.push(next[i]);
                } else {
                    level.push(this.concat(next[i], next[i + 1]));
                }
            }
            next = level;
        }
    }
    getProof(index, next = this.leaves){
        let proof = [];
        while (true) {
            if (next.length <= 1) {
                return proof;
            }
            let level = [];
            for (let i = 0; i < next.length; i += 2) {
                if ((i + 1) >= next.length) {
                    level.push(next[i]);
                } else {
                    level.push(this.concat(next[i], next[i + 1]));
                    if (index === i || i === (index - 1)) {
                        if (index === i) {
                            proof.push({data:next[i + 1], left:false});
                        } else {
                            proof.push({data:next[i], left:true});
                        }
                    }
                }
            }
            index = Math.floor(index/2);
            next = level;
        }
    }
}

module.exports = MerkleTree;

点击运行。

5: Verify your Proof

查看要求：

输入：

function verifyProof(proof, node, root, concat) {
    let n = node;
    proof.forEach((e,_) => {
        if (e.left) {
            n = concat(e.data, n);
        } else {
            n = concat(n, e.data);
        }
    });

    if (n === root) {
        return true;
    } else {
        return false;
    }
}

module.exports = verifyProof;

点击运行。

Learn Tries

1: Constructors

查看要求：

这里注意要改两个文件：

class TrieNode {
    constructor(key) {
        this.key = key;
        this.children = {};
        this.isWord = false;
    }
}

module.exports = TrieNode;

const TrieNode = require('./TrieNode');

class Trie {
    constructor() {
        this.root = new TrieNode(null);
    }
}

module.exports = Trie;

点击运行。

2: Insert

查看要求：

输入：

这里注意改第二个文件：

const TrieNode = require('./TrieNode');

class Trie {
    constructor() {
        this.root = new TrieNode(null);
    }

    insert(data) {
        let n = this.root;
        for (let i = 0; i < data.length; i++) {
            let node = new TrieNode(data[i]);
            n.children[data[i]] = node;
            if ((i + 1) === data.length) {
                node.isWord = true;
            }
            n = node;
        }
    }
}

module.exports = Trie;

点击运行。

3: Insert Branching

查看要求：

这里还是改这个文件：

输入：

const TrieNode = require('./TrieNode');

class Trie {
    constructor() {
        this.root = new TrieNode(null);
    }

    insert(data) {
        let n = this.root;
        for (let i = 0; i < data.length; i++) {
            let node = n.children[data[i]];
            if (! node) {
                node = new TrieNode(data[i]);
            }
            n.children[data[i]] = node;
            if ((i + 1) === data.length) {
                node.isWord = true;
            }
            n = node;
        }
    }
}

module.exports = Trie;

点击运行。

4: Contains

查看要求：

还是改这个文件，输入：

const TrieNode = require('./TrieNode');

class Trie {
    constructor() {
        this.root = new TrieNode(null);
    }

    insert(data) {
        let n = this.root;
        for (let i = 0; i < data.length; i++) {
            let node = n.children[data[i]];
            if (! node) {
                node = new TrieNode(data[i]);
            }
            n.children[data[i]] = node;
            if ((i + 1) === data.length) {
                node.isWord = true;
            }
            n = node;
        }
    }

    contains(word) {
        let n = this.root.children[word[0]];
        if (n === null) {
            return false;
        }
        let i = 1;
        while(n) {
            if (i >= word.length) {
                if (n.isWord) {
                    return true;
                } else {
                    return false;
                }
            }
            n = n.children[word[i]];
            if (n === null) {
                return false;
            }
            i = i + 1;
        }
    }
}

module.exports = Trie;

点击运行。

以上，Blockchain Storage，课程学习完成。

未完待续……

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