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

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

Description

You are given a binary array nums.

You can do the following operation on the array any number of times (possibly zero):

  • Choose any 3 consecutive elements from the array and flip all of them.

Flipping an element means changing its value from 0 to 1, and from 1 to 0.

Return the minimum number of operations required to make all elements in nums equal to 1. If it is impossible, return -1.

Example 1:

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Input: nums = [0,1,1,1,0,0]

Output: 3

Explanation:

We can do the following operations:

  • Choose the elements at indices 0, 1 and 2. The resulting array is nums = [1 ,0 ,0 ,1,0,0].
  • Choose the elements at indices 1, 2 and 3. The resulting array is nums = [1,1 ,1 ,0 ,0,0].
  • Choose the elements at indices 3, 4 and 5. The resulting array is nums = [1,1,1,1 ,1 ,1 ].

Example 2:

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Input: nums = [0,1,1,1]

Output: -1

Explanation:

It is impossible to make all elements equal to 1.

Constraints:

  • 3 <= nums.length <= 10^5
  • 0 <= nums[i] <= 1

Hints/Notes

  • Biweekly Contest 133

Solution

Language: C++

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class Solution {
public:
    int minOperations(vector<int>& nums) {
        int numOps = 0;
        for (int i = 0; i < nums.size() - 2; i++) {
            if (nums[i] == 0) {
                nums[i + 1] ^= 1;
                nums[i + 2] ^= 1;
                numOps++;
            }
        }
        int size = nums.size();
        return nums[size - 2] && nums[size - 1] ? numOps : -1;
    }
};