ClosestPrimeNumbersInRange.java

import java.util.Arrays;

public class ClosestPrimeNumbersInRange {
    int N = 1000000;
    int[] prime = new int[N];
    public void sieve() {
        Arrays.fill(prime, 1);
        prime[0] = 0;
        prime[1] = 0;
        for (int i = 2; i * i < N; i++) {
            if (prime[i] == 1) {
                for (int j = i * i; j < N; j += i) {
                    prime[j] = 0;
                }
            }
        }
    }
    public int[] closestPrimes(int left, int right) {
        sieve();
        int[] ans = {-1, -1};
        int prev = -1;
        int minDiff = Integer.MAX_VALUE;
        for (int i = left; i <= right; i++) {
            if (prime[i] == 0)
                continue;
            if (prev != -1) {
                int diff = i - prev;
                if (diff < minDiff) {
                    minDiff = diff;
                    ans[0] = prev;
                    ans[1] = i;
                }
            }
            prev = i;
        }
        return ans;
    }
}