1248 - Count Number of Nice Subarrays

 JAVA

• class Solution {
      public int numberOfSubarrays(int[] nums, int k) {
          int n = nums.length;
          int[] cnt = new int[n + 1];
          cnt[0] = 1;
          int ans = 0, t = 0;
          for (int v : nums) {
              t += v & 1;
              if (t - k >= 0) {
                  ans += cnt[t - k];
              }
              cnt[t]++;
          }
          return ans;
      }
  }

C++

• class Solution {
  public:
      int numberOfSubarrays(vector<int>& nums, int k) {
          int n = nums.size();
          vector<int> cnt(n + 1);
          cnt[0] = 1;
          int ans = 0, t = 0;
          for (int& v : nums) {
              t += v & 1;
              if (t - k >= 0) {
                  ans += cnt[t - k];
              }
              cnt[t]++;
          }
          return ans;
      }
  };