README.md

1969. Minimum Non-Zero Product of the Array Elements

You are given a positive integer p. Consider an array nums (1-indexed) that consists of the integers in the inclusive range [1, 2p - 1] in their binary representations. You are allowed to do the following operation any number of times:

• Choose two elements x and y from nums.
• Choose a bit in x and swap it with its corresponding bit in y. Corresponding bit refers to the bit that is in the same position in the other integer.

For example, if x = 1101 and y = 0011, after swapping the 2nd bit from the right, we have x = 1111 and y = 0001.

Find the minimum non-zero product of nums after performing the above operation any number of times. Return this product modulo 109 + 7.

Note: The answer should be the minimum product before the modulo operation is done.

Example 1:

Input: p = 1
Output: 1
Explanation: nums = [1].
There is only one element, so the product equals that element.

Example 2:

Input: p = 2
Output: 6
Explanation: nums = [01, 10, 11].
Any swap would either make the product 0 or stay the same.
Thus, the array product of 1 * 2 * 3 = 6 is already minimized.

Example 3:

Input: p = 3
Output: 1512
Explanation: nums = [001, 010, 011, 100, 101, 110, 111]
- In the first operation we can swap the leftmost bit of the second and fifth elements.
    - The resulting array is [001, 110, 011, 100, 001, 110, 111].
- In the second operation we can swap the middle bit of the third and fourth elements.
    - The resulting array is [001, 110, 001, 110, 001, 110, 111].
The array product is 1 * 6 * 1 * 6 * 1 * 6 * 7 = 1512, which is the minimum possible product.

Constraints:

• 1 <= p <= 60

Solutions (Rust)

1. Solution

impl Solution {
    pub fn min_non_zero_product(p: i32) -> i32 {
        let x = 2_u64.pow(p as u32) % 1_000_000_007;

        ((x - 1) * Self::power(x - 2, 2_u64.pow(p as u32 - 1) - 1) % 1_000_000_007) as i32
    }

    fn power(x: u64, exp: u64) -> u64 {
        if exp == 0 {
            1
        } else if exp % 2 == 0 {
            let y = Self::power(x, exp / 2);
            y * y % 1_000_000_007
        } else {
            x * Self::power(x, exp - 1) % 1_000_000_007
        }
    }
}