LeetCode每日一题(2447. Number of Subarrays With GCD Equal to K)

Given an integer array nums and an integer k, return the number of subarrays of nums where the greatest common divisor of the subarray’s elements is k.

A subarray is a contiguous non-empty sequence of elements within an array.

The greatest common divisor of an array is the largest integer that evenly divides all the array elements.

Example 1:

Input: nums = [9,3,1,2,6,3], k = 3
Output: 4

Explanation: The subarrays of nums where 3 is the greatest common divisor of all the subarray’s elements are:

• [9,3,1,2,6,3]
• [9,3,1,2,6,3]
• [9,3,1,2,6,3]
• [9,3,1,2,6,3]

Example 2:

Input: nums = [4], k = 7
Output: 0

Explanation: There are no subarrays of nums where 7 is the greatest common divisor of all the subarray’s elements.

Constraints:

• 1 <= nums.length <= 1000
• 1 <= nums[i], k <= 109

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欧几里得最大公约数计算方法 + 去重优化

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use std::collections::{BinaryHeap, HashSet};

impl Solution {
    fn calc_gcd(nums: &HashSet<i32>) -> i32 {
        let mut heap = BinaryHeap::new();
        let mut min = i32::MAX;
        for &n in nums {
            if n == 1 {
                return 1;
            }
            min = min.min(n);
            heap.push(n);
        }
        while let Some(n) = heap.pop() {
            let r = n % min;
            if r == 0 {
                continue;
            }
            min = min.min(r);
            heap.push(r);
        }
        min
    }

    pub fn subarray_gcd(nums: Vec<i32>, k: i32) -> i32 {
        let mut ans = 0;
        for i in 0..nums.len() {
            if nums[i] % k != 0 {
                continue;
            }
            let mut set = HashSet::new();
            set.insert(nums[i]);
            for j in i..nums.len() {
                set.insert(nums[j]);
                if Solution::calc_gcd(&set) == k {
                    ans += 1;
                }
            }
        }
        ans
    }
}