2495. Number of Subarrays Having Even Product

Description

Given a 0-indexed integer array nums, return the number of subarrays of nums having an even product.

 

Example 1:

Input: nums = [9,6,7,13]
Output: 6
Explanation: There are 6 subarrays with an even product:
- nums[0..1] = 9 * 6 = 54.
- nums[0..2] = 9 * 6 * 7 = 378.
- nums[0..3] = 9 * 6 * 7 * 13 = 4914.
- nums[1..1] = 6.
- nums[1..2] = 6 * 7 = 42.
- nums[1..3] = 6 * 7 * 13 = 546.

Example 2:

Input: nums = [7,3,5]
Output: 0
Explanation: There are no subarrays with an even product.

 

Constraints:

  • 1 <= nums.length <= 105
  • 1 <= nums[i] <= 105

Solutions

Solution 1

Python Code
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class Solution:
    def evenProduct(self, nums: List[int]) -> int:
        ans, last = 0, -1
        for i, v in enumerate(nums):
            if v % 2 == 0:
                last = i
            ans += last + 1
        return ans

Java Code
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class Solution {
    public long evenProduct(int[] nums) {
        long ans = 0;
        int last = -1;
        for (int i = 0; i < nums.length; ++i) {
            if (nums[i] % 2 == 0) {
                last = i;
            }
            ans += last + 1;
        }
        return ans;
    }
}

C++ Code
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class Solution {
public:
    long long evenProduct(vector<int>& nums) {
        long long ans = 0;
        int last = -1;
        for (int i = 0; i < nums.size(); ++i) {
            if (nums[i] % 2 == 0) {
                last = i;
            }
            ans += last + 1;
        }
        return ans;
    }
};

Go Code
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func evenProduct(nums []int) int64 {
	ans, last := 0, -1
	for i, v := range nums {
		if v%2 == 0 {
			last = i
		}
		ans += last + 1
	}
	return int64(ans)
}