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Say I have an array already with these articles, ordered by lowest to highest price:
[
{ title: "Article 3", price: 1.49 },
{ title: "Article 1", price: 3.00 },
{ title: "Article 4", price: 5.99 },
{ title: "Article 2", price: 19.99 }
]
Basically I would like to push another article into the array at the correct position (by price). How can I do so?
The new article I'm pushing may have the following properties:
{ title: "Article 5", price: 12.00 }
I'm expecting the article to appear at index 3 (between article 4 and 2).
I created a prototype method using @klutt's answer with binary search algorithm:
Array.prototype.pushSorted = function(el, compareFn) {
this.splice((function(arr) {
var m = 0;
var n = arr.length - 1;
while(m <= n) {
var k = (n + m) >> 1;
var cmp = compareFn(el, arr[k]);
if(cmp > 0) m = k + 1;
else if(cmp < 0) n = k - 1;
else return k;
}
return -m - 1;
})(this), 0, el);
return this.length;
};
const sortByPrice = (a, b) => a.price > b.price;
theArray.pushSorted({ title: "Article 5", price: 12.00 }, sortByPrice);
464
You want to explicitly add it at a particular place of the array. That place is called the index. Array indexes start from 0 , so if you want to add the item first, you'll use index 0 , in the second place the index is 1 , and so on. To perform this operation you will use the splice() method of an array.
In order to insert an element in the specific index, we need to provide the arguments as: start → the index in which to insert the element. deleteCount → 0 (because we don't need to delete any elements). elem → elements to insert.
To insert element in an array sorted in ascending order,First compare the elements which is to be inserted(num) with every elements of array from start, if num is greater than elements of array increament the position. And when the num become less than any element insert num to that position.
The unshift() method adds new elements to the beginning of an array. The unshift() method overwrites the original array.
The Update (Solution) still doesn't work great. Items that should go either to the start or end get placed in the wrong position, see this revised solution based on the same code:
Array.prototype.pushSorted = function(el, compareFn) {
let index = (function(arr) {
var m = 0;
var n = arr.length - 1;
while(m <= n) {
var k = (n + m) >> 1;
var cmp = compareFn(el, arr[k]);
if(cmp > 0) m = k + 1;
else if(cmp < 0) n = k - 1;
else {
console.log(`m=${m} k=${k}`)
return k;
};
}
return -m - 1;
})(this);
if (index >= 0)
this.splice(index, 0, el);
else if (index < 0)
this.splice((index * -1) - 1, 0, el);
return this.length;
};
Sample usage:
a = [1, 2, 3, 4, 5]
a.pushSorted(2.5, (a,b) => a - b);
a.pushSorted(8, (a,b) => a - b);
a.pushSorted(0.5, (a,b) => a - b);
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