leetcode/leet225.cpp at main · JaydeepRokade/leetcode · GitHub

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class Solution {
public:
    vector<int> closestPrimes(int left, int right) {
        vector<bool> sieve(right + 1, true);
        sieve[0] = sieve[1] = false;

        for (int i = 2; i * i <= right; ++i) {
            if (sieve[i]) {
                for (int j = i * i; j <= right; j += i) {
                    sieve[j] = false;
                }
            }
        }

        vector<int> primes;
        for (int i = left; i <= right; ++i) {
            if (sieve[i]) {
                primes.push_back(i);
            }
        }

        if (primes.size() < 2) {
            return {-1, -1};
        }

        int min_gap = INT_MAX;
        vector<int> result = {-1, -1};

        for (int i = 1; i < primes.size(); ++i) {
            int gap = primes[i] - primes[i - 1];
            if (gap < min_gap) {
                min_gap = gap;
                result = {primes[i - 1], primes[i]};
            }
        }

        return result;
    }
};