如何在数组中的值之前和之后添加值 [英] How to add a value in an array to the values before and after it

问题描述

我正在尝试将数字数组转换为非零整数元素的值的步长，即

I am trying to turn an array of numbers into steps of the value of the Non-Zero integer element i.e

spread([0,0,n,0,0] returns => 
[0 + n-2, 0 + n-1, n, 0 + n -1, 0 + n - 2]

spread([0,0,0,n,0,2]) returns => 
[0+n-3, 0+n-2, 0+n-1, n ,(2-1)+(n-1) ,2 + n-2]

spread([0,0,0,4,0,0,0]) returns => [1,2,3,4,3,2,1]

spread([0,0,0,3,0,2,0]) returns => [0,1,2,3,3,3,1]

spread([3,0,0,0]) returns => [3,2,1,0]

等。

我尝试了传统的for循环，我尝试了forEach，甚至是array.map，但没有按预期工作

I have tried the traditional for loop, i have tried forEach, even array.map but nothing works as expected

这是我尝试过的方法，但不起作用

Here is what I tried but it doesn't work

function pop(balloon) {
  let res = [];

  for (let i = 0; i < balloon.length; i++) {

    let n = balloon[i];
    let before = balloon[i - 1];
    let after = balloon[i + 1];

    if (n !== 0 && i < balloon.length - 1) {
      res.push(before + n - 1);
      res.push(n);
      res.push(after + n - 1);

    } else {
      res.push(n);
    }

  }
  return res;
}

const array1 = [0, 0, 0, 0, 4, 0, 0, 3, 0]
const array2 = [0, 0, 2, 0, 0]

console.log(pop(array1)) // returns[0, 0, 0, 0, 3, 4, 3, 0, 0, 2, 3, 2, 0]
// expected output => [0, 1, 2, 3, 4, 4, 4, 4, 2]

console.log(pop(array2)) // returns[0, 0, 1, 2, 1, 0, 0]
// expected output => [0, 1, 2, 1, 0]

推荐答案

您可以通过使用数组的副本来缩小数组，并使用递归函数左右移动该递归函数，以检查要散布的值和索引。

You could reduce the array by using a copy of the array and go left and right with a recursive function which checks the value to spread and the index.

function spread(array) {
    return array.reduce((r, v, i, a) => {
        const
            iter = (v, i, d) => {
                if (v < 1 || !(i in a)) return;
                r[i] += v;
                iter(v - 1, i + d, d);
            };
        iter(v - 1, i - 1, -1);
        iter(v - 1, i + 1, 1);
        return r;
    }, array.slice());
}

console.log(...spread([0, 0, 0, 4, 0, 0, 0])); // [1, 2, 3, 4, 3, 2, 1]
console.log(...spread([0, 0, 0, 3, 0, 2, 0])); // [0, 1, 2, 3, 3, 3, 1]
console.log(...spread([3, 0, 0, 0]));          // [3, 2, 1, 0]

function spread(array) {
    const dec = v => Math.max(v - 1, 0);

    var result = array.slice(),
        temp = array.slice(1).map(v => Math.max(v - 1, 0)),
        offset;
    
    while (temp.length) {
        temp.forEach((v, i) => result[i] += v);
        temp = temp.slice(1).map(dec);
    }

    temp = array.slice(0, -1).map(dec);
    while (temp.length) {
        offset = result.length - temp.length;
        temp.forEach((v, i) => result[i + offset] += v);
        temp = temp.slice(0, -1).map(dec);
    }
    return result;
}

console.log(...spread([0, 0, 0, 4, 0, 0, 0])); // [1, 2, 3, 4, 3, 2, 1]
console.log(...spread([0, 0, 0, 3, 0, 2, 0])); // [0, 1, 2, 3, 3, 3, 1]
console.log(...spread([3, 0, 0, 0]));          // [3, 2, 1, 0]

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