[20250310] BOJ / P3 / 소가 길을 건너간 이유 10 / 권혁준

khj20006/202503/10 BOJ P3 소가 길을 건너간 이유 10.md

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+```java
+
+import java.util.*;
+import java.io.*;
+
+class SegTree{
+	long[] tree;
+	SegTree(int size){
+		tree = new long[size*4];
+	}
+	void upt(int s, int e, int i, int v, int n) {
+		if(s == e) {
+			tree[n] = v;
+			return;
+		}
+		int m=(s+e)>>1;
+		if(i <= m) upt(s,m,i,v,n*2);
+		else upt(m+1,e,i,v,n*2+1);
+		tree[n] = tree[n*2] + tree[n*2+1];
+	}
+	long find(int s, int e, int l, int r, int n) {
+		if(l>r || l>e || r<s) return 0;
+		if(l<=s && e<=r) return tree[n];
+		int m=(s+e)>>1;
+		return find(s,m,l,r,n*2) + find(m+1,e,l,r,n*2+1);
+	}
+}
+
+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 int[] A, B, P, Q;
+	static SegTree seg;
+
+	public static void main(String[] args) throws Exception {
+
+		ready();
+		solve();
+
+		bwEnd();
+
+	}
+
+	static void ready() throws Exception{
+
+		N = Integer.parseInt(br.readLine());
+		A = new int[N+1];
+		B = new int[N+1];
+
+		for(int i=1;i<=N;i++) A[i] = Integer.parseInt(br.readLine());
+		for(int i=1;i<=N;i++) B[i] = Integer.parseInt(br.readLine());
+
+	}
+
+	static void solve() throws Exception{
+
+		long ans = Math.min(result(A,B), result(B,A));
+
+		bw.write(ans + "\n");
+
+	}
+
+	static long result(int[] a, int[] b) {
+
+		P = new int[N+1];
+		Q = new int[N+1];
+		for(int i=1;i<=N;i++) {
+			int x = a[i];
+			P[x] = i;
+		}
+
+		seg = new SegTree(N+1);
+		long res = 0;
+
+		for(int i=1;i<=N;i++) {
+			int x = b[i];
+			Q[i] = P[x];
+			res += seg.find(1, N, P[x], N, 1);
+			seg.upt(1, N, P[x], 1, 1);
+		}
+
+		long ans = res;
+		for(int i=N;i>=1;i--) {
+			res = (res - (N-Q[i]) + Q[i]-1);
+			ans = Math.min(ans, res);
+		}
+
+		return ans;
+
+	}
+
+}
+
+```