Generate merged array from a string by multiple positions of the string

Question

For example,

const text = "APPLE ORANGE";
const text_position = [0,4,4,7,9];
const inserted_value = ["yo","wo","go","lo","zo"];

For this example, I would like to create an array like this:

return ["yo","APPL","wo","go","E O","lo","RA","zo","NGE"];

My code:

I am trying to merge into an array from a given string by an array of string positions. There are one string and two arrays given:

const content = "0123456789TEXT";
const footnote_position  = [0, 1, 2, 2, 6]; // string positions 
const footnote_value = ["ZERO", "ONE", "TWO", "TWO", "SIX"]; // inserted values

But for my code and above given content, footnote_position, and footnote_value, the algorithm must output as follow:

["ZEROR","0","ONE","1","TWO","TWO","2345","SIX","67899TEXT"]

My complete code is:

const content = "0123456789TEXT";
const footnote_position = [0, 1, 2, 2, 6]; // must be sorted
const footnote_value = ["ZERO", "ONE", "TWO", "TWO", "SIX"];

const position_set = [...new Set(footnote_position)]; // must be sorted 1,2,6
const contentArray = [];


let textArray = [];
let prev = -1;
let count = footnote_position.length;


for (let index = 0; index < count + 1; index++) {

  switch (index) {

    case 0: // ok
      var item = footnote_position[index];
      if (item != 0) {
        textArray.push(content.substring(0, item));
      }
      footnote_position.forEach((value, position) => {
        if (value == item) {
          textArray.push(footnote_value[position]);

        }
      })
      prev = item;
      break;
    case length: // ok
      textArray.push(content.substring(prev)); // <Text>
      footnote_position.forEach((value, position) => {
        if (value == item) textArray.push(footnote_value[position]);
      })
      break;
    default: // not ok
      var item = footnote_position[index];
      textArray.push(content.substring(prev, item));
      footnote_position.forEach((value, position) => {
        if (value == item) textArray.push(footnote_value[position]);
      })
      prev = item;
      break;
  }
}

console.log(textArray);

Unfortunately, my output is different as follows:

["ZERO", "0", "ONE", "1", "TWO", "TWO", "", "TWO", "TWO", "2345", "SIX", "6789TEXT"]

What went wrong? Do you have any alternative different algorithm solution for this problem?

Plus, I really have no idea why case length: is working. There is no defined variable length in the code.

I really don't understand the logic behind this algorithm from the given example. Do you mind explaining it? — msmolcic
– msmolcic, Commented Aug 12, 2020 at 8:22
Yes, I added one example, could you please re-read the question? @msmolcic — Nay Sie
– Nay Sie, Commented Aug 12, 2020 at 8:38

Siva Kondapi Venkata · Accepted Answer · 2020-08-12 10:40:43Z

3

Use forEach, slice and maintain last

Update: Fixing the issue of last element. Great suggestion @mplungjan and Thank you.

const text = "APPLE ORANGE";
const text_position = [0, 4, 4, 7, 9];
const inserted_value = ["yo", "wo", "go", "lo", "zo"];

let last = 0;
const output = [];
text_position.forEach((index, i) => {
  const value = text.slice(last, index);
  if (value) {
    output.push(value);
  }

  output.push(inserted_value[i]);
  last = index;
});
if (last < text.length) output.push(text.slice(last));

console.log(output);

Alternate way using flatMap

const text = "APPLE ORANGE";
const text_position = [0, 4, 4, 7, 9];
const inserted_value = ["yo", "wo", "go", "lo", "zo"];

let last = 0;
const output = text_position.flatMap((index, i) => {
  const output = [];
  last < index && output.push(text.slice(last, index));
  output.push(inserted_value[i]);
  last = index;
  (i === (text_position.length - 1)) && (last < text.length) && output.push(text.slice(last));
  return output;
})

console.log(output);

edited Aug 12, 2020 at 10:40

answered Aug 12, 2020 at 8:56

Siva Kondapi Venkata

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5 Comments

Nay Sie Over a year ago

Almost there, your result is [ "yo", "APPL", "wo", "go", "E O", "lo", "RA", "zo" ] and expected result is [ "yo", "APPL", "wo", "go", "E O", "lo", "RA", "zo", "NGE" ]

mplungjan Over a year ago

If the NGE is fixed, then this is the more elegant solution. I worked on similar, but had already a working example in place

Nay Sie Over a year ago

I agree with @mplungjan

mplungjan Over a year ago

Just add if (last < text.length) output.push(text.slice(last)) before the end

Siva Kondapi Venkata Over a year ago

Ah, right I missed that @mplungjan, Nay Sie. Thank you very much. :)

mplungjan · Accepted Answer · 2020-08-12 08:56:42Z

1

I rewrote the code to handle your second example

const mergeIt = (content, posArr, valArr) => {
  const arr = content.split("");
  posArr.sort((a, b) => a - b); // must be sorted
  while (posArr.length) {
    const pos = posArr.pop(); // destructive - you may want to clone
    const val = valArr.pop(); // destructive - you may want to clone
    if (val !== null) arr.splice(pos, 0, `|${val}|`);
  }
  return arr.join("").split("|").filter(w => w)
};

let content = "0123456789TEXT";
let footnote_position = [2, 1, 0, 2, 6];
let footnote_value = ["ZERO", "ONE", "TWO", "TWO", "SIX"];
console.log(mergeIt(content, footnote_position, footnote_value))


const text = "APPLE ORANGE";
const text_position = [0, 4, 4, 7, 9];
const inserted_value = ["yo", "wo", "go", "lo", "zo"];
console.log(mergeIt(text, text_position, inserted_value))

// returns  ["yo","APPL","wo","go","E O","lo","RA","zo","NGE"]

edited Aug 12, 2020 at 8:56

answered Aug 12, 2020 at 8:25

mplungjan

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3 Comments

Nay Sie Over a year ago

Almost there, I added one example in the question for more clarification. Could you please re-read the post again?

Nay Sie Over a year ago

Wow, thank you very much for your time and your help. It works now.

mplungjan Over a year ago

It is not as elegant as the other solution but the other solution needs to add any missing strings to the array

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