[백준 21757] 나누기 - DP

Author: HiiWee

hoseok/week80/Boj21757.java

@@ -0,0 +1,43 @@
+import java.io.*;
+import java.util.*;
+
+class Main {
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        int n = Integer.parseInt(br.readLine());
+        int[] arr = new int[n + 1];
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        for (int i = 1; i <= n; i++) {
+            arr[i] = Integer.parseInt(st.nextToken());
+            arr[i] += arr[i - 1];
+        }
+
+        long[] dp = new long[4];
+        dp[0] = 1;
+
+        long answer = 0;
+        if (arr[n] == 0) {
+            long count = 0;
+            for (int i = 1; i <= n; i++) {
+                if (arr[i] == 0) {
+                    count++;
+                }
+            }
+            answer = (count - 1) * (count - 2) * (count - 3) / 6;
+        } else if (arr[n] % 4 == 0) {
+            int target = arr[n] / 4;
+            for (int i = 1; i <= n; i++) {
+                int count = arr[i] / target;
+                if (arr[i] % target == 0 && count > 0 && count < 4) {
+                    dp[count] += dp[count - 1];
+                }
+            }
+            answer = dp[3];
+        }
+
+        bw.write(Long.toString(answer));
+        bw.flush();
+        bw.close();
+    }
+}