查找数组中每个数字的第一次出现

Question

依次取数组中的每个四位数，当发现所有0-9的数字时，返回您所处的数字。如果不能找到所有的数字，返回"缺少的数字">

我试过循环然后设置一个有条件的if (I != I +1)推入新的数组，这只是给了我数组，很明显我的逻辑是错误的。有人能帮我吗?

例如用

调用这个函数

arr = findAllDigits([5175, 4538, 2926, 5057, 6401, 4376, 2280, 6137, 8798, 9083]) 

代码应该返回5057。

时调用

arr = findAllDigits([4883, 3876, 7769, 9846, 9546, 9634, 9696, 2832, 6822, 6868]) 

应该返回"缺少的数字">

function findAllDigits(arr) {
newArr = [];
for (let i = 0; i < arr.length; i++) {
if (arr[i] != arr[i + 1]) newArr.push(arr[i]);
console.log(newArr);
}
}

我是否需要分割，因为它将逗号之前的所有内容作为一个数字，然后迭代?

Answer 1

可以在这里使用Set

循环array，然后创建一个set，如果set的大小变成10，你必须返回当前的数字，因为你需要检查0-9

function findAllDigits(arr) {
const set = new Set();
for (let n of arr) {
String(n)
.split("")
.forEach((c) => set.add(c));
if (set.size === 10) return n;
}
return "Missing digits!";
}
const arr1 = [5175, 4538, 2926, 5057, 6401, 4376, 2280, 6137, 8798, 9083];
const arr2 = [4883, 3876, 7769, 9846, 9546, 9634, 9696, 2832, 6822, 6868];
console.log(findAllDigits(arr1));
console.log(findAllDigits(arr2));

Answer 2

for循环只是检查数组条目是否等于下一个。您需要拆分每个条目中的数字并单独存储它们:

function findAllDigits(arr) {
newArr = [];
for (let i = 0; i < arr.length; i++) {
// now iterate the individual digits
const entryAsString = arr[i].toString();
for (let j = 0; j < entryAsString.length; j++) {
// if we haven't seen the digit before, add it to the array
if(!newArr.includes(j) {
newArr.push(j);
}
}
// we know we have all digits when newArr is 10 entries long
if (newArr.length) {
console.log(arr[i]);
// you can also return this value here
}
}
}

Answer 3

又一个解决方案:

const arr1 = [5175, 4538, 2926, 5057, 6401, 4376, 2280, 6137, 8798, 9083];
const arr2 = [4883, 3876, 7769, 9846, 9546, 9634, 9696, 2832, 6822, 6868];

const findAllDigits = (arr) => {
// Declare new Set: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set
const digits = new Set();
// return the first item from array that fits the condition, 
// find() method: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
return arr.find((curr) => (
// String(5175) -> '5175' : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String
// [...'5175'] ->  ['5','1','7','5'] : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax
// .forEach(digits.add, digits) - forEach with callback function and context : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
// comma operator lets get rid of return : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator
[...String(curr)].forEach(digits.add, digits),
// condition - is find() method need to return an item  
(digits.size === 10)

// if returned value is not undefined or null return finded number oterwise error string
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator
)) ?? "Missing digits!";
};

console.log(findAllDigits(arr1)); //5057
console.log(findAllDigits(arr2)); //Missing digits!