[20250308] BOJ / G2 / MEX / 권혁준

khj20006/202503/08 BOJ G2 MEX.md

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+## JAVA
+```java
+
+import java.util.*;
+import java.io.*;
+
+
+class Main {
+
+	// IO field
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	static StringTokenizer st;
+
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static int nextInt() {return Integer.parseInt(st.nextToken());}
+	static long nextLong() {return Long.parseLong(st.nextToken());}
+	static void bwEnd() throws Exception {bw.flush();bw.close();}
+
+	// Additional field
+
+	static int N;
+    static boolean[] A = new boolean[2200001];
+    static boolean[] B = new boolean[2200001];
+
+	public static void main(String[] args) throws Exception {
+
+		ready();
+		solve();
+
+		bwEnd();
+
+	}
+
+	static void ready() throws Exception{
+
+		N = Integer.parseInt(br.readLine());
+        for(nextLine();N-->0;A[nextInt()]=true);
+
+	}
+
+	static void solve() throws Exception{
+
+		for(int i=0;i<=2200000;i++) {
+            if(!A[i] && !B[i]){
+                bw.write(i + "\n");
+                return;
+            }
+            if(i<2 || !A[i]) continue;
+            for(long j=i*2;j<=Math.min(2200000L,(long)i*i);j+=i) B[(int)j] = true;
+        }
+
+	}
+
+}
+
+```
+
+## C++
+```cpp
+
+#include <iostream>
+#include <bitset>
+using namespace std;
+using ll = long long;
+
+int main() {
+    cin.tie(0)->sync_with_stdio(0);
+
+    int N;
+    cin>>N;
+    bitset<2200001> A, B;
+    for(int a;N--;A[a]=1) cin>>a;
+    for(int i=0;i<2200001;i++) {
+        if(!A[i] && !B[i]) return cout<<i,0;
+        if(i < 2 || !A[i]) continue;
+        for(ll j=i*2;j<=min(2200000LL, (ll)i*i);j+=i) B[j] = 1;
+    }
+
+}
+
+```