[Combination] baekjoon-1256

Author: Seogeurim

README.md

@@ -71,4 +71,5 @@
 | :-: | :----: | :------------------------------------------------------------------------------------------------------------------ | :------------------------ |
 | 01  |     | [Baekjoon-11050 이항 계수 1](https://github.com/Seogeurim/Algorithm-practice/blob/master/src/Combination/P11050) |      |
 | 02  |     | [Baekjoon-11051 이항 계수 2](https://github.com/Seogeurim/Algorithm-practice/blob/master/src/Combination/P11051) | DP   |
-| 03  |     | [Baekjoon-1010 다리 놓기](https://github.com/Seogeurim/Algorithm-practice/blob/master/src/Combination/P1010) |      |
+| 03  |     | [Baekjoon-1010 다리 놓기](https://github.com/Seogeurim/Algorithm-practice/blob/master/src/Combination/P1010) | DP     |
+| 04  | ⭐️ | [Baekjoon-1256 사전](https://github.com/Seogeurim/Algorithm-practice/blob/master/src/Combination/P1256) |        |

src/Combination/P1256/Main.java

@@ -0,0 +1,76 @@
+package Combination.P1256;
+
+import java.io.BufferedReader;
+import java.io.FileInputStream;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+public class Main {
+
+    static int[][] combis = new int[202][202];
+    static int MAX = 1000000000;
+
+    static int N, M, K;
+    static int aCase, zCase;
+
+    public static void main(String[] args) throws Exception {
+//        System.setIn(new FileInputStream("src/Combination/P1256/input.txt"));
+
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        K = Integer.parseInt(st.nextToken());
+
+        if (K > comb(N + M, N)) {
+            System.out.println(-1);
+        } else {
+            StringBuilder sb = new StringBuilder();
+            while (N + M > 0) {
+                if (N == 0 || M == 0) {
+                    break;
+                }
+                aCase = comb(N + M - 1, N - 1);
+                zCase = comb(N + M - 1, M - 1);
+                if (K <= aCase) {
+                    sb.append("a");
+                    N--;
+                } else {
+                    sb.append("z");
+                    M--;
+                    K -= aCase;
+                }
+            }
+
+            for (int i = 0; i < N; i++) {
+                sb.append('a');
+            }
+            for (int i = 0; i < M; i++) {
+                sb.append('z');
+            }
+            System.out.println(sb);
+        }
+    }
+
+    static int comb(int n, int k) {
+        if (combis[n][k] != 0)
+            return combis[n][k];
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 0; j <= k; j++) {
+                if (i == j || j == 0){
+                    combis[i][j] = 1;
+                } else {
+                    long result = combis[i-1][j-1] + combis[i-1][j];
+                    if (result > MAX)
+                        combis[i][j] = MAX;
+                    else
+                        combis[i][j] = (int) result;
+                }
+            }
+        }
+
+        return combis[n][k];
+    }
+}

src/Combination/P1256/README.md

@@ -0,0 +1,15 @@
+
+🚩 다음 코드 간결화 시키기 (계산한 숫자가 10억이 넘어가면 10억으로 치환해주는 코드)
+10억 : `1e9`로 표현할 수 있다.
+
+```java
+long result = combis[i-1][j-1] + combis[i-1][j];
+if (result > MAX)
+    combis[i][j] = MAX;
+else
+    combis[i][j] = (int) result;
+```
+
+```java
+combis[i][j] = Math.min(combis[i-1][j-1] + combis[i-1][j], (int) 1e9);
+```

src/Combination/P1256/input.txt

@@ -0,0 +1 @@
+2 3 7