Leetcode no. 330

330. 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]

inclusive 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

.

public class Solution {
public int minPatches(int[] nums, int n) {
long cover=1;
int count=0, i=0;
while (cover<= n){
if (i< nums.length && cover>= nums[i])
cover+= nums[i++];
else {
count++;
cover+= cover;
}
}
return count;
}
}