1646. Get Maximum in Generated Array

1. Question

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.

2. Examples

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.

3. Constraints

• 0 <= n <= 100

4. References

来源：力扣（LeetCode） 链接：https://leetcode-cn.com/problems/get-maximum-in-generated-array 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

5. Solutions

递归

class Solution {
    public int getMaximumGenerated(int n) {
        int[] arr = new int[n + 2];
        arr[0] = 0;
        arr[1] = 1;
        if (n < 2) {
            return arr[n];
        }
        for (int i = 2; i < arr.length - 1; i++) {
            if (i % 2 == 0) {
                arr[i] = arr[i / 2];
            } else {
                arr[i] = arr[i / 2] + arr[i / 2 + 1];
            }
        }
        return Arrays.stream(arr).max().getAsInt();
    }
}