JavaScript Searching and Sorting Algorithm: Sorted last index
JavaScript Searching and Sorting Algorithm: Exercise-23 with Solution
Write a JavaScript program to find the highest index at which a value should be inserted into an array in order to maintain its sort order.
- Loosely check if the array is sorted in descending order.
- Use Array.prototype.reverse() and Array.prototype.findIndex() to find the appropriate last index where the element should be inserted.
Sample Solution:
JavaScript Code:
const sortedLastIndex = (arr, n) => {
const isDescending = arr[0] > arr[arr.length - 1];
const index = arr
.reverse()
.findIndex(el => (isDescending ? n <= el : n >= el));
return index === -1 ? 0 : arr.length - index;
};
console.log(sortedLastIndex([10, 20, 30, 30, 40], 30));
Sample Output:
4
Flowchart:
Live Demo:
See the Pen javascript-common-editor by w3resource (@w3resource) on CodePen.
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JavaScript: Tips of the Day
How to insert an item into an array at a specific index (JavaScript)?
What you want is the splice function on the native array object.
arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:
var arr = []; arr[0] = "Jani"; arr[1] = "Hege"; arr[2] = "Stale"; arr[3] = "Kai Jim"; arr[4] = "Borge"; console.log(arr.join()); arr.splice(2, 0, "Lene"); console.log(arr.join());
Ref: https://bit.ly/2BXbp04
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