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:

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

Rust Solution

struct Solution;

impl Solution {
    fn min_patches(nums: Vec<i32>, n: i32) -> i32 {
        let mut res = 0;
        let mut miss: i64 = 1;
        let mut i = 0;
        while miss <= n as i64 {
            if i < nums.len() && nums[i] as i64 <= miss {
                miss += nums[i] as i64;
                i += 1;
            } else {
                miss += miss;
                res += 1;
            }
        }
        res
    }
}

#[test]
fn test() {
    let nums = vec![1, 3];
    let n = 6;
    let res = 1;
    assert_eq!(Solution::min_patches(nums, n), res);
    let nums = vec![1, 5, 10];
    let n = 20;
    let res = 2;
    assert_eq!(Solution::min_patches(nums, n), res);
    let nums = vec![1, 2, 2];
    let n = 5;
    let res = 0;
    assert_eq!(Solution::min_patches(nums, n), res);
}

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