查找数组中每个数字的第一次出现

Question

依次取数组的每个四位数字，当找到所有数字 0-9 时，返回您所在的数字。如果无法找到所有数字，则返回“缺少数字！”

我尝试循环然后设置条件 if (i != i+1) push into new array 这只是给了我数组，很明显我的逻辑是错误的。谁能帮帮我

例如调用这个函数

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

代码应该返回 5057。

打电话时

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

应该返回“缺失的数字”

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);
  }
}

我是否需要拆分，因为它将逗号之前的所有内容都视为 一个数字，然后迭代？

Answer 1

你可以在这里使用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

您的 for 循环只是检查数组条目是否等于下一个条目。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

另一种解决方案：

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!