使用哈希检查 3 个数组之间是否存在重复产品

Question

我有一个产品列表，其数据已拆分为 3 个数组，其中包含产品的名称、价格和重量。如何创建使用哈希映射查找重复产品的函数？

//Inputs:
name = ["ball", "bat", "glove", "glove", "glove"]
price = [2, 3, 1, 2, 1]
weight = [2, 5, 1, 1, 1]
//Output: true

//Inputs: 
name = ["ball", "bat", "glove", "glove", "glove"]
price = [2, 3, 1, 2, 2]
weight = [2, 5, 1, 1, 2]
//Output: false

Answer 1

我会首先质疑将数据拆分为三个数组的需要，然后如果无法重塑数据结构，则最终以这种方式解决问题。

const findDupes = (
  [name, ...names], 
  [price, ...prices], 
  [weight, ...weights], 
  res = {},
) => {
  const next = ($res) => findDupes(names, prices, weights, $res);
  const hash = `${name}\/${price}\/${weight}`;
  
  const dupe = res[hash] ? { name, price, weight } : [];
  
  return [].concat(dupe).concat(
    names.length ? next({ ...res, [hash]: true }) : [],
  );
};

const name = ["ball", "bat", "glove", "glove", "glove"];
const price = [2, 3, 1, 2, 1];
const weight = [2, 5, 1, 1, 1];

console.log(
  findDupes(name, price, weight),
);

Answer 2

Javascript 没有 HashSet，但有一个 Set 可以存储任何你喜欢的东西。因此，要测试重复项：

创建一个空的Set
遍历 i = 0..items.length
对于每个 i，从 name[i]、price[i] 和 weight[i] 创建一个散列。注意：你怎么做并不重要，只要满足以下条件（注意 3x ===）：

hash(name[i], price[i], weight[i]) === hash(name[i], price[i], weight[i])
创建哈希后，检查它是否已经存在于您的 Set
- 如果存在，则存在重复，您可以立即return
- 如果没有，则将散列添加到集合中并继续循环
不提前到达循环末尾return意味着没有重复

let name, price, weight;

const makeHash = (name, price, weight) => 
  `${name}__${price}__${weight}`;
  
const duplicateTest = () => {
  const seen = new Set();
  
  for (let i = 0; i < name.length; i += 1) {
    const hash = makeHash(name[i], price[i], weight[i]);
    if (seen.has(hash)) return true;
    
    seen.add(hash);
  }
  
  return false;
}


name = ["ball", "bat", "glove", "glove", "glove"]
price = [2, 3, 1, 2, 1]
weight = [2, 5, 1, 1, 1]
console.log(duplicateTest()); // Output: true

name = ["ball", "bat", "glove", "glove", "glove"]
price = [2, 3, 1, 2, 2]
weight = [2, 5, 1, 1, 2]
console.log(duplicateTest()); // Output: false

使用哈希检查 3 个数组之间是否存在重复产品

Check if there is a duplicate product between 3 arrays using hash

javascript

hash

functional-programming

hashtable

hashmap