[20250311] BOJ / P3 / 빵 정렬 / 권혁준

khj20006/202503/11 BOJ P3 빵 정렬.md

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+```java
+
+import java.util.*;
+import java.io.*;
+
+class SegTree{
+	int[] tree;
+	SegTree(int size){
+		tree = new int[size*4 + 1];
+	}
+	void upt(int s, int e, int i, int n) {
+		if(s == e) {
+			tree[n]++;
+			return;
+		}
+		int m=(s+e)>>1;
+		if(i<=m) upt(s,m,i,n*2);
+		else upt(m+1,e,i,n*2+1);
+		tree[n] = tree[n*2] + tree[n*2+1];
+	}
+	int 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, pos;
+	static boolean[] vis;
+	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];
+		pos = new int[N+1];
+		vis = new boolean[N+1];
+		seg = new SegTree(N);
+
+		nextLine();
+		for(int i=1;i<=N;i++) {
+			int a = nextInt();
+			A[i] = a;
+			pos[a] = i;
+		}
+
+	}
+
+	static void solve() throws Exception{
+
+		int s = 1, e = 2;
+		nextLine();
+		for(int i=1;i<=N-2;i++) {
+			int b = nextInt();
+			int p = pos[b] - seg.find(1, N, 1, pos[b], 1);
+			vis[b] = true;
+			while(vis[A[s]]) s++;
+			while(vis[A[e]] || s >= e) e++;
+			seg.upt(1, N, pos[b], 1);
+			if(p%2 != 0) continue;
+			int temp = pos[A[s]];
+			pos[A[s]] = pos[A[e]];
+			pos[A[e]] = temp;
+			temp = A[s];
+			A[s] = A[e];
+			A[e] = temp;
+		}
+
+		int p = nextInt(), q = nextInt();
+		if(p == A[s] && q == A[e]) bw.write("Possible");
+		else bw.write("Impossible");
+
+	}
+
+}
+
+```