**Leetcode Q330. Patching Array (Q278)**

Given a sorted integer array nums and an integer n, add/patch elements to the array such that any number in the 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

**Constraints:**

1 <= nums.length <= 1000

1 <= nums[i] <= 10⁴

nums is sorted in ascending order.

1 <= n <= 2³¹ — 1

**Complexity:**

Time: O(n)

Space: O(1)

**Code:**

/**

* @param {number[]} nums

* @param {number} n

* @return {number}

*/

var minPatches = function(nums, n) {

let ans = 0;

let i = 0;

let miss = 1;

while (miss <= n)

if (i < nums.length && nums[i] <= miss) {

miss += nums[i++];

} else {

miss += miss;

++ans;

}

return ans;

};

minPatches([1, 3], 6)

**O/P:**

1