[백준 2407] 조합 - DP

Author: minnim1010

minji/개인문제풀이/조합.java

@@ -0,0 +1,81 @@
+import java.io.IOException;
+import java.math.BigInteger;
+
+public class Main {
+    private static int N;
+    private static int M;
+    private static BigInteger answer;
+
+    public static void main(String[] args) throws Exception {
+        input();
+
+        answer = solution();
+
+        output();
+    }
+
+    private static BigInteger solution() {
+        BigInteger[] multiplyResult = new BigInteger[101];
+
+        multiplyResult[1] = BigInteger.ONE;
+        for (int i = 2; i <= N; i++) {
+            multiplyResult[i] = multiplyResult[i-1].multiply(BigInteger.valueOf(i));
+        }
+
+        return multiplyResult[N].divide(multiplyResult[N-M]).divide(multiplyResult[M]);
+    }
+
+    private static void input() throws Exception {
+        N = readInt();
+        M = readInt();
+    }
+
+    private static void output() {
+        System.out.println(answer);
+    }
+
+    static int readInt() throws IOException {
+        int val = 0;
+        boolean negative = false;
+
+        while (true) {
+            int c = System.in.read();
+            if (c == ' ' || c == '\n' || c == -1) {
+                break;
+            }
+            if (c == '-') {
+                negative = true;
+                continue;
+            }
+            val = 10 * val + c - 48;
+        }
+
+        return negative ? -val : val;
+    }
+}
+
+/**
+ * public class Main {
+ *
+ * 	public static void main(String[] args) {
+ * 		try {
+ * 			BufferedReader br = new BufferedReader(new InputStreamReader(System.in), 1);
+ * 			String[] sp = br.readLine().split(" ");
+ * 			int n = Integer.parseInt(sp[0]);
+ * 			int m = Integer.parseInt(sp[1]);
+ *
+ * 			BigInteger res = fact(n).divide(fact(m).multiply(fact(n-m)));
+ * 			System.out.println(res);
+ *                } catch (IOException e) {
+ * 			e.printStackTrace();
+ *        }* 	}
+ *
+ * 	public static BigInteger fact(int n) {
+ * 		BigInteger bi = new BigInteger("1");
+ * 		for (int i = 1; i <= n; i++) {
+ * 			bi = bi.multiply(BigInteger.valueOf(i));
+ *        }
+ * 		return bi;* 	}
+ * }
+ * https://www.acmicpc.net/source/6335406
+ */