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

Problem Statement

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

Medium

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:

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:

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

Output: -1

Explanation:
It is impossible to make all elements equal to 1.

Constraints:

3 <= nums.length <= 10⁵
0 <= nums[i] <= 1

Java

Source file

class Solution {
    public int minOperations(int[] nums) {
        int n = nums.length, lt = 0, rt = 2, flips = 0;
        while (rt < n) {
            if (nums[lt] == 0) {
                nums[lt] = 1;
                nums[lt + 1] = 1 - nums[lt + 1];
                nums[rt] = 1 - nums[rt];
                flips++;
            }
            lt++;
            rt++;
        }
        return ((nums[rt - 1] & nums[rt - 2]) & nums[rt - 3]) == 0 ? -1 : flips;
    }
}