Leet Code Daily 2024-06-22 - Count Number of Nice Subarrays

class Solution {
public:
    int numberOfSubarrays(vector<int>& nums, int k) {

        vector<int> sums = {0};
        unordered_map<int, int> cnt;
        cnt[0]++;

        int ans = 0;
        for (const auto& num : nums) {
            const int sum = sums.back() + (num % 2);
            sums.push_back(sum);
            if (sum - k >= 0) {
                ans += cnt[sum - k];
            }
            cnt[sum]++;
        }
        return ans;
    }
};