2996. Smallest Missing Integer Greater Than Sequential Prefix Sum

class Solution {
    public int missingInteger(int[] nums) {
        int n = nums.length;
        int sum = nums[0];
        int i = 1;
        while (i < n && nums[i] == nums[i - 1] + 1) {
            sum += nums[i];
            i++;
        }

        Set<Integer> set = new HashSet<>();
        for (int num : nums) {
            set.add(num);
        }

        while (set.contains(sum)) {
            sum++;
        }

        return sum;
    }
}

By CodeByTushu

class Solution:
    def missingInteger(self, nums):
        n = len(nums)

        # Find the longest sequential prefix
        total = nums[0]
        i = 1

        while i < n and nums[i] == nums[i - 1] + 1:
            total += nums[i]
            i += 1

        # Store all numbers in a set
        seen = set(nums)

        # Find the smallest missing integer
        while total in seen:
            total += 1

        return total

class Solution {
public:
    int missingInteger(vector<int>& nums) {
        int n = nums.size();

        // Find the longest sequential prefix
        int sum = nums[0];
        int i = 1;

        while (i < n && nums[i] == nums[i - 1] + 1) {
            sum += nums[i];
            i++;
        }

        // Store all numbers in a set
        unordered_set<int> seen(nums.begin(), nums.end());

        // Find the smallest missing integer
        while (seen.count(sum)) {
            sum++;
        }

        return sum;
    }
};

class Solution {
    missingInteger(nums) {
        const n = nums.length;

        // Find the longest sequential prefix
        let sum = nums[0];
        let i = 1;

        while (i < n && nums[i] === nums[i - 1] + 1) {
            sum += nums[i];
            i++;
        }

        // Store all numbers in a Set
        const seen = new Set(nums);

        // Find the smallest missing integer
        while (seen.has(sum)) {
            sum++;
        }

        return sum;
    }
}