Tuesday, March 26, 2024

 You are given a 0-indexed integer array nums of length n.

You can perform the following operation as many times as you want:

Pick an index i that you haven’t picked before, and pick a prime p strictly less than nums[i], then subtract p from nums[i].

Return true if you can make nums a strictly increasing array using the above operation and false otherwise.

A strictly increasing array is an array whose each element is strictly greater than its preceding element.

 

Example 1:

Input: nums = [4,9,6,10]

Output: true

Explanation: In the first operation: Pick i = 0 and p = 3, and then subtract 3 from nums[0], so that nums becomes [1,9,6,10].

In the second operation: i = 1, p = 7, subtract 7 from nums[1], so nums becomes equal to [1,2,6,10].

After the second operation, nums is sorted in strictly increasing order, so the answer is true.

Example 2:

Input: nums = [6,8,11,12]

Output: true

Explanation: Initially nums is sorted in strictly increasing order, so we don't need to make any operations.

Example 3:

Input: nums = [5,8,3]

Output: false

Explanation: It can be proven that there is no way to perform operations to make nums sorted in strictly increasing order, so the answer is false.

 

Constraints:

1 <= nums.length <= 1000

1 <= nums[i] <= 1000

nums.length == n

class Solution {

    public boolean primeSubOperation(int[] nums) {

        for (int i = 0; i < nums.length; i++) {

            int min = 0;

            if (i > 1) min = Math.max(nums[i-1], 0);

            int max = nums[i];

            int prime = getPrime(min, max);

            nums[i] -= prime;

        }

        return isIncreasing(nums);   

    }

    public boolean isIncreasing(int[] nums){

        for (int i = 1; i < nums.length; i++){

            if (nums[i] <= nums[i-1]){

                return false;

            }

        }

        return true;

    }

    public int getPrime(int min, int max) {

        for (int i = max-1; i > min; i--){

            if (isPrime(i) && (max – i > min)){

                return i;

            }

        }

        return 0;

    }

    public boolean isPrime(int n){

        for (int i = 2; i < n; i++){

            if (n % i == 0) {

                return false;

            }

        }

        return true;

    }

}


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