Formatted question description: https://leetcode.ca/all/1909.html

1909. Remove One Element to Make the Array Strictly Increasing

Level

Easy

Description

Given a 0-indexed integer array nums, return true if it can be made strictly increasing after removing exactly one element, or false otherwise. If the array is already strictly increasing, return true.

The array nums is strictly increasing if nums[i - 1] < nums[i] for each index (1 <= i < nums.length).

Example 1:

Input: nums = [1,2,10,5,7]

Output: true

Explanation: By removing 10 at index 2 from nums, it becomes [1,2,5,7]. [1,2,5,7] is strictly increasing, so return true.

Example 2:

Input: nums = [2,3,1,2]

Output: false

Explanation:

[3,1,2] is the result of removing the element at index 0.

[2,1,2] is the result of removing the element at index 1.

[2,3,2] is the result of removing the element at index 2.

[2,3,1] is the result of removing the element at index 3.

No resulting array is strictly increasing, so return false.

Example 3:

Input: nums = [1,1,1]

Output: false

Explanation: The result of removing any element is [1,1].

[1,1] is not strictly increasing, so return false.

Example 4:

Input: nums = [1,2,3]

Output: true

Explanation: [1,2,3] is already strictly increasing, so return true.

Constraints:

  • 2 <= nums.length <= 1000
  • 1 <= nums[i] <= 1000

Solution

For each index, try to remove the element at the index and check whether the remaining elements are strictly increasing. If there exists at least one element that makes the remaining elements strictly increasing, return true. Otherwise, return false.

If the array is already strictly increasing, then after removing any element, the remaining elements are also strictly increasing, so return true.

class Solution {
    public boolean canBeIncreasing(int[] nums) {
        int length = nums.length;
        for (int i = 0; i < length; i++) {
            if (isIncreasing(nums, i))
                return true;
        }
        return false;
    }

    public boolean isIncreasing(int[] nums, int index) {
        int length = nums.length;
        int prev = -1;
        for (int i = 0; i < length; i++) {
            if (i != index) {
                int curr = nums[i];
                if (curr <= prev)
                    return false;
                prev = curr;
            }
        }
        return true;
    }
}

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