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

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