LeetCode 2601. Prime Subtraction Operation

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

好尴尬啊，基本上每个函数都写错过，isprime函数漏写了1的情况，1不是质数，不是质数，不是质数。。。。

first_numSubtract()这个函数是将第一个元素先降低到最小值，

然后剩下的元素去每次判断是否存在num[i]-num[i-1]的质数，有的话，就将这个num[i]减去对应的质数，

还有个checksort的函数，判断是否是严格递增的，没错是严格递增，我以为>=就行了，不行，不行，不行，要>才行啊。。。

综上就是题意没理解透彻，另外就是基础不扎实，还需要多多锻炼，汗颜啊。。。

Runtime: 6 ms, faster than 90.91% of Java online submissions for Prime Subtraction Operation.

Memory Usage: 42.6 MB, less than 63.64% of Java online submissions for Prime Subtraction Operation.