330. Patching Array

• 題目 Given a sorted positive integer array nums and an integer n, add/patch elements to the array such that any number in range [1, n] inclusive can be formed by the sum of some elements in the array. Return the minimum number of patches required.

  Example 1:

  Input: nums = [1,3], n =
   
   6
  Output: 1 
  Explanation:
  Combinations of nums are [1], [3], [1,3], which form possible sums of: 1, 3, 4.
  Now if we add/patch 2 to nums, the combinations are: [1], [2], [3], [1,3], [2,3], [1,2,3].
  Possible sums are 1, 2, 3, 4, 5, 6, which now covers the range [1, 6].
  So we only need 1 patch.
  

  Example 2:

  Input: nums = [1,5,10], n = 20
  Output: 2
  Explanation: The two patches can be [2, 4].
  

  Example 3:

  Input: nums = [1,2,2], n = 5
  Output: 0
  

• 解題過程