[LeetCode] Patching Array

[LeetCode] Patching Array

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]Specified sive can be formed by the sum of some elements in the array. Return the minimum number of patches required.

Example 1:
Nums =[1, 3], N = 6
Return 1.

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:
Nums =[1, 5, 10], N = 20
Return 2.
The two patches can be[2, 4].

Example 3:
Nums =[1, 2, 2], N = 5
Return 0.

Solutions

Suppose the range that the array can currently represent is[1, total)To add elements to the array.addExtend the representation range[1, total + add), Whereadd≤total. When and only whenadd=totalMaximum time range[1, 2 * total).

When the array contains less than or equal addThe elements in the array are used. If no, add a new element. add. Implementation Code

//Runtime: 1 mspublic class Solution {    public int minPatches(int[] nums, int n) {        long miss = 1;        int add = 0;        int i = 0;        while (miss <= n) {            if (i < nums.length && nums[i] <= miss){                miss += nums[i++];            } else {                miss += miss;                add += 1;            }        }        return add;    }}