1646. Get Maximum in Generated Array

You are given an integer n. An array nums of length n + 1 is generated in the following way:

  • nums[0] = 0
  • nums[1] = 1
  • nums[2 * i] = nums[i] when 2 <= 2 * i <= n
  • nums[2 * i + 1] = nums[i] + nums[i + 1] when 2 <= 2 * i + 1 <= n

Return the maximum integer in the array nums​​​.

 

Example 1:

Input: n = 7
Output: 3
Explanation: According to the given rules:
  nums[0] = 0
  nums[1] = 1
  nums[(1 * 2) = 2] = nums[1] = 1
  nums[(1 * 2) + 1 = 3] = nums[1] + nums[2] = 1 + 1 = 2
  nums[(2 * 2) = 4] = nums[2] = 1
  nums[(2 * 2) + 1 = 5] = nums[2] + nums[3] = 1 + 2 = 3
  nums[(3 * 2) = 6] = nums[3] = 2
  nums[(3 * 2) + 1 = 7] = nums[3] + nums[4] = 2 + 1 = 3
Hence, nums = [0,1,1,2,1,3,2,3], and the maximum is 3.

Example 2:

Input: n = 2
Output: 1
Explanation: According to the given rules, the maximum between nums[0], nums[1], and nums[2] is 1.

Example 3:

Input: n = 3
Output: 2
Explanation: According to the given rules, the maximum between nums[0], nums[1], nums[2], and nums[3] is 2.

 

Constraints:

  • 0 <= n <= 100

Rust Solution

struct Solution;

impl Solution {
    fn get_maximum_generated(n: i32) -> i32 {
        if n == 0 {
            return 0;
        }
        let n = n as usize + 1;
        let mut arr = vec![0; n];
        arr[0] = 0;
        arr[1] = 1;
        for i in 2..n {
            if i % 2 == 0 {
                arr[i] = arr[i / 2];
            } else {
                arr[i] = arr[i / 2] + arr[i / 2 + 1];
            }
        }
        arr.into_iter().max().unwrap()
    }
}

#[test]
fn test() {
    let n = 7;
    let res = 3;
    assert_eq!(Solution::get_maximum_generated(n), res);
    let n = 2;
    let res = 1;
    assert_eq!(Solution::get_maximum_generated(n), res);
    let n = 3;
    let res = 2;
    assert_eq!(Solution::get_maximum_generated(n), res);
}

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