[20250213] BOJ / G5 / 시철이가 사랑한 GCD / 권혁준

khj20006/202502/13 BOJ G5 시철이가 사랑한 GCD.md

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+```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 long[] A;
+	static int N;
+
+	public static void main(String[] args) throws Exception {
+
+		ready();
+		solve();
+
+		bwEnd();
+	}
+
+	static void ready() throws Exception{
+
+		N = Integer.parseInt(br.readLine());
+		A = new long[N];
+		nextLine();
+		for(int i=0;i<N;i++) A[i] = nextLong();
+
+	}
+
+	static void solve() throws Exception{
+
+		bw.write(find(0,N-1) + "\n");
+
+	}
+
+	static long find(int s, int e) {
+		if(s == e) return A[s];
+		int m=(s+e-1)/2;
+		long left = A[s], right = A[e];
+		for(int i=s+1;i<=m;i++) left = gcd(left, A[i]);
+		for(int i=m+1;i<e;i++) right = gcd(right, A[i]);
+		return Math.max(left + find(m+1,e), right + find(s,m));
+	}
+
+	static long gcd(long a, long b) {
+		if(a < b) {
+			long temp = a;
+			a = b;
+			b = temp;
+		}
+		return a%b!=0 ? gcd(b,a%b) : b;
+	}
+
+}
+
+```