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3191. Minimum Operations to Make Binary Array Elements Equal to One I 👍

  • Time: $O(n)$
  • Space: $O(1)$
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class Solution {
 public:
  int minOperations(vector<int>& nums) {
    const int n = nums.size();
    int ans = 0;

    for (int i = 0; i + 2 < n; ++i)
      if (nums[i] == 0) {
        nums[i + 1] ^= 1;
        nums[i + 2] ^= 1;
        ++ans;
      }

    return nums[n - 1] == 0 || nums[n - 2] == 0 ? -1 : ans;
  }
};

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class Solution {
  public int minOperations(int[] nums) {
    final int n = nums.length;
    int ans = 0;

    for (int i = 0; i + 2 < n; ++i)
      if (nums[i] == 0) {
        nums[i + 1] ^= 1;
        nums[i + 2] ^= 1;
        ++ans;
      }

    return nums[n - 1] == 0 || nums[n - 2] == 0 ? -1 : ans;
  }
}

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class Solution:
  def minOperations(self, nums: list[int]) -> int:
    ans = 0

    for i in range(len(nums) - 2):
      if nums[i] == 0:
        nums[i + 1] ^= 1
        nums[i + 2] ^= 1
        ans += 1

    return -1 if nums[-1] == 0 or nums[-2] == 0 else ans