995 - Minimum Number of K Consecutive Bit Flips

 JAVA

• class Solution {
      public int minKBitFlips(int[] nums, int k) {
          int n = nums.length;
          int[] d = new int[n + 1];
          int ans = 0, s = 0;
          for (int i = 0; i < n; ++i) {
              s += d[i];
              if (nums[i] % 2 == s % 2) {
                  if (i + k > n) {
                      return -1;
                  }
                  ++d[i];
                  --d[i + k];
                  ++s;
                  ++ans;
              }
          }
          return ans;
      }
  }

C++

• class Solution {
  public:
      int minKBitFlips(vector<int>& nums, int k) {
          int n = nums.size();
          int d[n + 1];
          memset(d, 0, sizeof(d));
          int ans = 0, s = 0;
          for (int i = 0; i < n; ++i) {
              s += d[i];
              if (s % 2 == nums[i] % 2) {
                  if (i + k > n) {
                      return -1;
                  }
                  ++d[i];
                  --d[i + k];
                  ++s;
                  ++ans;
              }
          }
          return ans;
      }
  };