330. Patching Array.md

330. Patching Array

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leetcode-cn Daily Challenge on December 29th, 2020.

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Difficulty : Hard

Related Topics : Greedy

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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

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Solution

• mine
  • Java
    • ``

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• the most votes

• Runtime: 0 ms, faster than 100.00%, Memory Usage: 38.8 MB, less than 31.58% of Java online submissions

  public int minPatches(int[] nums, int n) {
      int patches = 0;
      long x = 1;
      int length = nums.length, index = 0;
      while (x <= n) {
          if (index < length && nums[index] <= x) {
              x += nums[index];
              index++;
          } else {
              x *= 2;
              patches++;
          }
      }
      return patches;
  }
  

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