[20250409] BOJ / P4 / 아 또 XOR이야? / 권혁준

Author: oncsr

khj20006/202504/09 BOJ P4 아 또 XOR이야?.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 = new StringTokenizer("");
+
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static String nextToken() throws Exception {
+		while(!st.hasMoreTokens()) nextLine();
+		return st.nextToken();
+	}
+	static int nextInt() throws Exception { return Integer.parseInt(nextToken()); }
+	static long nextLong() throws Exception { return Long.parseLong(nextToken()); }
+	static double nextDouble() throws Exception { return Double.parseDouble(nextToken()); }
+	static void bwEnd() throws Exception {bw.flush();bw.close();}
+	
+	// Additional field
+	
+	static long N, A, B;
+	static int K;
+	static long[][] C;
+	
+	public static void main(String[] args) throws Exception {
+		
+		ready();
+		solve();
+	
+		bwEnd();
+		
+	}
+	
+	static void ready() throws Exception{
+		
+		N = nextLong();
+		K = nextInt();
+		A = nextLong();
+		B = nextLong();
+		C = new long[62][62];
+		C[0][0] = 1;
+		for(int i=1;i<=61;i++) {
+			C[i][0] = 1;
+			for(int j=1;j<i;j++) C[i][j] = C[i-1][j-1] + C[i-1][j];
+			C[i][i] = 1;
+		}
+		
+	}
+	
+	static void solve() throws Exception{
+		
+		bw.write((f(N,K,B) - f(N,K,A-1)) + "\n");
+		
+	}
+	
+	static long f(long n, int k, long x) {
+		
+		if(x <= 0) return 0L;
+		long res = 0, d = 1L;
+		int nCount = bits(n);
+		int zero = 0, one = 0;
+		while((d<<1)-1 <= x) {
+			int cur = (n&d) != 0 ? 1 : 0;
+			nCount -= cur;
+			int temp = k - nCount - (cur^1);
+			
+			if(temp >= 0) {
+				for(int zeroSelect = 0;zeroSelect<=zero;zeroSelect++) {
+					int oneSelect = temp - zeroSelect;
+					if(oneSelect > one) continue;
+					if(oneSelect < 0) break;
+					res += C[zero][zeroSelect] * C[one][oneSelect];
+				}
+			}
+			
+			if(cur == 0) zero++;
+			else one++;
+			d<<=1;
+		}
+		if(x >= d) res += f(n^d, k, x-d) + (bits(n^d) == k ? 1 : 0);
+		return res;
+		
+	}
+	
+	static int bits(long x) {
+		int res = 0;
+		for(int i=0;i<=60;i++) res += (x & (1L<<i)) == 0 ? 0 : 1;
+		return res;
+	}
+	
+}
+
+```