What I am trying to achieve is somewhat like a radio group behavior, where only one radio input can be selected at a time. For example, the starting array [0, 1, 1, 1, 1, 1] should have its elements swapped in the following way:

I have come up with this, but I think it does "extra work" (unnecessary loops) in certain scenarios.

function rearrange(array: number[], idx: number) {
  let arr = array.slice();
  let l = arr.length;
  if (arr.indexOf(0) === idx) return arr;

  while (arr.indexOf(0) !== idx) {
    let swap;
    for (let i = 0; i < l; i  ) {
      if (arr[i] === 0 || arr[i   1] === 0) {
        swap = arr[i];
        if (i   1 < l) {
          arr[i] = arr[i   1];
          arr[i   1] = swap;
        }
        if (i   1 > l) {
          arr[i] = arr[i - 1];
          arr[i - 1] = swap;
        }
      }
    }
  }

  return arr;
}

I was wondering if you would have ideas on how to make this process simpler/better.

CodePudding user response：

Just identify the previous 0 with findIndex, assign 1 to it, and assign 0 to the idx?

function rearrange(array: number[], idx: number) {
  const arr = [...array];
  arr[arr.indexOf(0)] = 1;
  arr[idx] = 0;
  return arr;
}

Another approach...

const rearrange = (array: number[], idx: number) => (
  array.map((_, i) => i === idx ? 0 : 1)
);

CodePudding user response：

Instead of swapping pairs, you can rotate the subarray in "one go", using slice and splice.

Here is a function that does the job, mutating the given array (not returning a new one), together with a sequence of calls to demonstrate it. I assume values could be varying and need to stay together as if they were swapped with the "moving" 0:

function rearrange(array, idx) {
  let zero = array.indexOf(0);
  if (zero < idx) {
      arr.splice(zero, idx - zero   1, ...arr.slice(zero   1, idx   1), 0);
  } else {
      arr.splice(idx, zero - idx   1, 0, ...arr.slice(idx, zero));
  }
}

arr = [0,1,2,3,4,5];

rearrange(arr, 3);
console.log(...arr);
rearrange(arr, 1);
console.log(...arr);
rearrange(arr, 5);
console.log(...arr);
rearrange(arr, 1);
console.log(...arr);