javascript, better way for get indices of numrical array in decrsing order as new array - Stack Overflow

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I want JavaScript function, that receive an array as input and output the indices of the array in a order which if value is max it's index should be at [0] of new array, second max [1] and so on ...

for example: [3, 4, 5, 1, 2] as input should give [2,1,0,4,3] output

I code this function but I want a way with one for loop or one map function

const maxValueIndexes = (array) => {

    if (array.length === 0) return []; 
    
    const indexedArray = array.map((value, index) => ({value, index }));
    indexedArray.sort((a, b) => b.value - a.value);
    return indexedArray.map((item) => item.index);
}

Is there any better way in terms of time complexity ??

for example O(n) answer

if there is solution please write it for me

I want JavaScript function, that receive an array as input and output the indices of the array in a order which if value is max it's index should be at [0] of new array, second max [1] and so on ...

for example: [3, 4, 5, 1, 2] as input should give [2,1,0,4,3] output

I code this function but I want a way with one for loop or one map function

const maxValueIndexes = (array) => {

    if (array.length === 0) return []; 
    
    const indexedArray = array.map((value, index) => ({value, index }));
    indexedArray.sort((a, b) => b.value - a.value);
    return indexedArray.map((item) => item.index);
}

Is there any better way in terms of time complexity ??

for example O(n) answer

if there is solution please write it for me

• javascript
• arrays

Share Improve this question Follow edited 22 hours ago Areza-s1011 asked 23 hours ago Areza-s1011Areza-s1011 1555 bronze badges 3

• 1 Stack Overflow is a question and answer platform for specific questions. Do you have a specific question? "I want..." or "Write the code for me" aren't questions. – jabaa Commented 23 hours ago
• 1 thank you for your comment, will try to fix it – Areza-s1011 Commented 22 hours ago
• 3 "Is there any better way in terms of time complexity ??" No, probably not. .sort has a time complexity of at least O(n log n). The additional loops don't change anything. They have a time complexity of O(n). O(n log n + n) == O(n log n) + O(n) == O(n log n) – jabaa Commented 22 hours ago

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2 Answers 2

Sorted by: Reset to default 1

You could get the keys of the array and sort according of value.

(And yes, an interator is a loop.)

const
    array = [3, 4, 5, 1, 2],
    result = [...array.keys()].sort((i, j) => array[j] - array[i]);

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

If you want to achieve this with only one map, you can do it by maintaining a list of indices and sorting them based on the corresponding values in the array. Here's how you can do it with a single map function:

function getSortedIndices(arr) {
  return arr
    .map((_, index) => index) // Create an array of indices [0, 1, 2, ...]
    .sort((a, b) => arr[b] - arr[a]); // Sort indices based on the values in the original array
}

// Example usage:
const input = [3, 4, 5, 1, 2];
const output = getSortedIndices(input);
console.log(output); // Output: [2, 1, 0, 4, 3]

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