Question

我想在数组中选择一个元素，将其移动到另一个索引，然后将“中间”元素“移位/旋转”1。

想象一下拖放功能，如果索引from小于索引to，那么我想转移到左侧，否则转移到右侧。 / p>

输入：

let data = [ 0, 1, 2, 3, 4, 5, 6 ]

任务1： insertAndShift(data, 0, 3): Take element at index 0, shift indexes 1, 2, 3 to the left, and then insert index 0 at 3

预期输出：

[ 1, 2, 3, 0, 4, 5, 6 ]

任务2： insertAndShift(data, 3, 0) Take element at index 3, shift indexes 0, 1, 2 to the right and then insert index 3 at 0

预期输出：

[ 0, 1, 2, 3, 4, 5, 6 ]

我试过了：

关注Rotating an array in place，丑陋且无法正常工作的代码（temp总是未定义+结果不完整+可能仅适用于RIGHT）：

insertAndShift(data, from, to)
{
    if(from < to)
    {
        // rotate in between - LEFT

    }
    else
    {    
        // swap elements
        let temp = data[from];
        data[from] = data[to];
        data[to] = temp;

        // rotate in between - RIGHT
        let newData = this.rotate(data.slice(to, from - 1), 1)

        let result = [];
        result.push(data.slice(0,1));
        newData.map((element) => result.push(element))
        for(let i = from+1; i < data.length; i++)
        {
            result.push(data[i]);
        }

        this.setState({data: result})
    }
}

rotate(arr, k) {
    var l = arr.length;
    arr = this.reverseArr(arr, 0, l - 1);
    arr = this.reverseArr(arr, 0, k - 1);
    arr = this.reverseArr(arr, k, l - 1);
    return arr;
}

reverseArr(arr, left, right) {
    while (left < right) {
        var temp = arr[left];
        arr[left] = arr[right];
        arr[right] = temp;
        left++;
        right--;
    }
    return arr;
}

同样关注Javascript (dynamic) insert into array, then shift all elements underneath +1，它只返回1项：

else
{
    let result = data.splice(to, 1, data[from]);
    this.setState({allTasksArray: result})
}

如何实现左右两种效果？

Answer 1

您可以使用Array.prototype.splice剪切出您想要的元素并插入所需的索引（移动将自动进行）：

function insertAndShift(arr, from, to) {
    let cutOut = arr.splice(from, 1) [0]; // cut the element at index 'from'
    arr.splice(to, 0, cutOut);            // insert it at index 'to'
}



let data = [ 0, 1, 2, 3, 4, 5, 6 ];

insertAndShift(data, 0, 3);
console.log("[" + data + "]");

insertAndShift(data, 3, 0);
console.log("[" + data + "]");

Answer 2

看看这种方法：Array.prototype.copyWithin()。

有一种更有效的就地方法：

function insertAndShift(data, src, dest) {
    if (src === dest)
        return;

    let tmp = data[src];
    if (src < dest) {
        data.copyWithin(src, src + 1, dest + 1);
    } else /* if (src > dest) */ {
        data.copyWithin(dest + 1, dest, src);
    }
    data[dest] = tmp;
}

let data = [0, 1, 2, 3, 4, 5, 6];

insertAndShift(data, 0, 3);
console.log("[" + data + "]");

insertAndShift(data, 3, 0);
console.log("[" + data + "]");

下面是一个例子：

Case 1 (src < dest):
[..Sabcd..]
    ////       // data.copyWithin(src, src+1, dest+1);
[..abcdd..]
[..abcdS..]    // data[dest] = tmp;

Case 2 (src > dest):
[..abcdS..]
    \\\\       // data.copyWithin(dest+1, dest, src);
[..aabcd..]
[..Sabcd..]    // data[dest] = tmp;

Answer 3

上面的答案很好用，但是有点麻烦……如果您对阐明其作用的解决方案感兴趣，我会这样写：

const insertAndShift = (arr: number[], to: number, from: number) => {
  let newArray: number[] = [];
  const fromItem = arr[from];
  if (from > to) {
    const startToTo = (to > 0) ? arr.slice(0, to) : [];
    const toToFrom = arr.slice(to, from);
    const fromToEnd = arr.slice(from + 1, arr.length);
    newArray = newArray.concat(startToTo, [fromItem], toToFrom, fromToEnd);
  }
  if (to > from) {
    const startToFrom = (from > 0) ? arr.slice(0, from) : [];
    const fromToTo = arr.slice(from + 1, to + 1);
    const toToEnd = arr.slice(to + 1, arr.length);
    newArray = newArray.concat(startToFrom, fromToTo, fromItem, toToEnd);
  }
  return newArray;
};

const array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

console.log(insertAndShift(array, 9, 0));
console.log(insertAndShift(array, 5, 1));

更改数组中的元素位置，并在其间移动元素

3 个答案: