You are given an integer array nums of even length n and an integer limit. In one move, you can replace any integer from nums with another integer between 1 and limit, inclusive.
The array nums is complementary if for all indices i (0-indexed), nums[i] + nums[n - 1 - i] equals the same number. For example, the array [1,2,3,4] is complementary because for all indices i, nums[i] + nums[n - 1 - i] = 5.
Return the minimum number of moves required to make nums complementary.
Example 1:
Input: nums = [1,2,4,3], limit = 4 Output: 1 Explanation: In 1 move, you can change nums to [1,2,2,3] (underlined elements are changed). nums[0] + nums[3] = 1 + 3 = 4. nums[1] + nums[2] = 2 + 2 = 4. nums[2] + nums[1] = 2 + 2 = 4. nums[3] + nums[0] = 3 + 1 = 4. Therefore, nums[i] + nums[n-1-i] = 4 for every i, so nums is complementary.
Example 2:
Input: nums = [1,2,2,1], limit = 2 Output: 2 Explanation: In 2 moves, you can change nums to [2,2,2,2]. You cannot change any number to 3 since 3 > limit.
Example 3:
Input: nums = [1,2,1,2], limit = 2 Output: 0 Explanation: nums is already complementary.
Constraints:
n == nums.length2 <= n <= 1051 <= nums[i] <= limit <= 105n is even.struct Solution;
impl Solution {
fn min_moves(nums: Vec<i32>, limit: i32) -> i32 {
let n = nums.len();
let limit = limit as usize;
let mut delta = vec![0; limit * 2 + 2];
for i in 0..n / 2 {
let a = nums[i] as usize;
let b = nums[n - 1 - i] as usize;
delta[2] += 2;
delta[a.min(b) + 1] -= 1;
delta[a + b] -= 1;
delta[a + b + 1] += 1;
delta[a.max(b) + limit + 1] += 1;
}
let mut res = std::i32::MAX;
let mut cur = 0;
for sum in 2..=limit * 2 {
cur += delta[sum];
res = res.min(cur);
}
res
}
}
#[test]
fn test() {
let nums = vec![1, 2, 4, 3];
let limit = 4;
let res = 1;
assert_eq!(Solution::min_moves(nums, limit), res);
let nums = vec![1, 2, 2, 1];
let limit = 2;
let res = 2;
assert_eq!(Solution::min_moves(nums, limit), res);
let nums = vec![1, 2, 1, 2];
let limit = 2;
let res = 0;
assert_eq!(Solution::min_moves(nums, limit), res);
}