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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

  • 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;
        }
    }
    
  • 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;
        }
    };
    
  • 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
    
    
  • 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)
    }
    

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