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Grzegorz Kućmierz

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Maximum Product of Three Numbers

Leetcode problem

Implementation

``````const maxProduct = arr => {
if (arr.length < 3) return false;
const max3 = [-Infinity, -Infinity, -Infinity];
const min2 = [Infinity, Infinity];

for (let i = 0; i < arr.length; ++i) {
const n = arr[i];
if (n > max3[0]) {
max3[0] = n;
max3.sort((a, b) => a - b);
}
if (n < min2[0]) {
min2[0] = n;
min2.sort((a, b) => b - a);
}
}
return max3[2] * Math.max(min2[0] * min2[1], max3[0] * max3[1]);
};
``````

Complexity

Time complexity: O(n)
Space complexity: O(1)

Explanation

Loop through array, while keeping 3 max elements and 2 min elements.
We want 2 min elements because min element can have bigger absolute value. When we calculating product always 2 negative numbers give 1 positive, so we need only 2 min to check if their product is not bigger that 2 smaller numbers of our 3 max.

My github reference

https://github.com/gkucmierz/algorithms/blob/master/problems/maximum_product_of_three_numbers.js

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