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            "title": "Count Array Pairs Divisible by K",
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            "content": "<p>Given a <strong>0-indexed</strong> integer array <code>nums</code> of length <code>n</code> and an integer <code>k</code>, return <em>the <strong>number of pairs</strong></em> <code>(i, j)</code> <em>such that:</em></p>\n\n<ul>\n\t<li><code>0 &lt;= i &lt; j &lt;= n - 1</code> <em>and</em></li>\n\t<li><code>nums[i] * nums[j]</code> <em>is divisible by</em> <code>k</code>.</li>\n</ul>\n\n<p>&nbsp;</p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [1,2,3,4,5], k = 2\n<strong>Output:</strong> 7\n<strong>Explanation:</strong> \nThe 7 pairs of indices whose corresponding products are divisible by 2 are\n(0, 1), (0, 3), (1, 2), (1, 3), (1, 4), (2, 3), and (3, 4).\nTheir products are 2, 4, 6, 8, 10, 12, and 20 respectively.\nOther pairs such as (0, 2) and (2, 4) have products 3 and 15 respectively, which are not divisible by 2.    \n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [1,2,3,4], k = 5\n<strong>Output:</strong> 0\n<strong>Explanation:</strong> There does not exist any pair of indices whose corresponding product is divisible by 5.\n</pre>\n\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>\n\t<li><code>1 &lt;= nums[i], k &lt;= 10<sup>5</sup></code></li>\n</ul>\n",
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                    "code": "class Solution {\npublic:\n    long long countPairs(vector<int>& nums, int k) {\n        \n    }\n};",
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                    "code": "class Solution {\n    public long countPairs(int[] nums, int k) {\n        \n    }\n}",
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                    "code": "class Solution(object):\n    def countPairs(self, nums, k):\n        \"\"\"\n        :type nums: List[int]\n        :type k: int\n        :rtype: int\n        \"\"\"\n        ",
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                    "code": "class Solution:\n    def countPairs(self, nums: List[int], k: int) -> int:\n        ",
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                    "code": "public class Solution {\n    public long CountPairs(int[] nums, int k) {\n        \n    }\n}",
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                    "code": "/**\n * @param {number[]} nums\n * @param {number} k\n * @return {number}\n */\nvar countPairs = function(nums, k) {\n    \n};",
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                    "code": "# @param {Integer[]} nums\n# @param {Integer} k\n# @return {Integer}\ndef count_pairs(nums, k)\n    \nend",
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                    "code": "class Solution {\n    func countPairs(_ nums: [Int], _ k: Int) -> Int {\n        \n    }\n}",
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                    "code": "object Solution {\n    def countPairs(nums: Array[Int], k: Int): Long = {\n        \n    }\n}",
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                    "code": "impl Solution {\n    pub fn count_pairs(nums: Vec<i32>, k: i32) -> i64 {\n        \n    }\n}",
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                "For any element in the array, what is the smallest number it should be multiplied with such that the product is divisible by k?",
                "The smallest number which should be multiplied with nums[i] so that the product is divisible by k is k / gcd(k, nums[i]). Now think about how you can store and update the count of such numbers present in the array efficiently."
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