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Total number of longest increasing sequences in JavaScript
Problem
We are required to write a JavaScript function that takes in an array of numbers, arr, as the first and the only argument.
Our function is required to find the number of longest increasing subsequences (contiguous or non-contiguous).
For example, if the input to the function is
Input
const arr = [2, 4, 6, 5, 8];
Output
const output = 2;
Output Explanation
The two longest increasing subsequences are [2, 4, 5, 8] and [2, 4, 6, 8].
Example
Following is the code −
const arr = [2, 4, 6, 5, 8];
const countSequence = (arr) => {
const distance = new Array(arr.length).fill(1).map(() => 1)
const count = new Array(arr.length).fill(1).map(() => 1)
let max = 1
for (let i = 0; i < arr.length; i++) {
for (let j = i + 1; j < arr.length; j++) {
if (arr[j] > arr[i]) {
if (distance[j] <= distance[i]) {
distance[j] = distance[i] + 1
count[j] = count[i]
max = Math.max(distance[j], max)
} else if (distance[j] === distance[i] + 1) {
count[j] += count[i]
}
}
}
}
return distance.reduce((acc, d, index) => {
if (d === max) {
acc += count[index]
}
return acc
}, 0)
}
console.log(countSequence(arr));Output
2
Updated on: 24-Apr-2021
650 Views
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