JavaScript: Create an array of prefix sums of the given array

Last update on May 30 2022 10:01:11 (UTC/GMT +8 hours)

JavaScript Basic: Exercise-131 with Solution

Write a JavaScript program to create an array of prefix sums of the given array.

In computer science, the prefix sum, cumulative sum, inclusive scan, or simply scan of a sequence of numbers x0, x1, x2, ... is a second sequence of numbers y0, y1, y2, ..., the sums of prefixes of the input sequence:
y0 = x0
y1 = x0 + x1
y2 = x0 + x1+ x2
...

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>Create an array of prefix sums of the given array</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function prefix_sums(arr) {
  var new_arr = [];
  for (var i = 0; i < arr.length; i++) {
    new_arr[i] = 0;
    for (var j = 0; j < i + 1; j++) {
      new_arr[i] += arr[j];
    }
  }
  return new_arr;
}

console.log(prefix_sums([1, 2, 3, 4, 5]));

console.log(prefix_sums([1, 2, -3, 4, 5]));

Sample Output:

[1,3,6,10,15]
[1,3,0,4,9]

Flowchart:

ES6 Version:

function prefix_sums(arr) {
  const new_arr = [];
  for (let i = 0; i < arr.length; i++) {
    new_arr[i] = 0;
    for (let j = 0; j < i + 1; j++) {
      new_arr[i] += arr[j];
    }
  }
  return new_arr;
}

console.log(prefix_sums([1, 2, 3, 4, 5]));

console.log(prefix_sums([1, 2, -3, 4, 5]));

Live Demo:

See the Pen javascript-basic-exercise-131 by w3resource (@w3resource) on CodePen.

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Next: Write a JavaScript program to find all distinct prime factors of a given integer.

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