[20251215] BOJ / G3 / 벌레컷 / 한종욱

Author: Ukj0ng

Ukj0ng/202512/15 BOJ G3 벌레컷.md

@@ -0,0 +1,79 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static int[] arr;
+    private static long[] sum;
+    private static int N;
+    private static long answer;
+
+    public static void main(String[] args) throws IOException {
+        init();
+        for (int i = 0; i < N-1; i++) {
+            int max = upperBound(i);
+            int min = lowerBound(i);
+
+            if (max != -1 && min != -1 && min <= max) {
+                answer += (max-min+1);
+            }
+        }
+
+        bw.write(answer + "\n");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        N = Integer.parseInt(br.readLine());
+        arr = new int[N];
+        sum = new long[N];
+
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        for (int i = 0; i < N; i++) {
+            arr[i] = Integer.parseInt(st.nextToken());
+            if (i == 0) sum[i] = arr[i];
+            else sum[i] = sum[i-1]+arr[i];
+        }
+    }
+
+    private static int upperBound(int head) {
+        int left = head+1;
+        int right = N-2;
+        int result = -1;
+
+        while (left <= right) {
+            int mid = left + (right-left)/2;
+
+            if (sum[head] < (sum[N-1]-sum[mid])) {
+                result = mid;
+                left = mid+1;
+            } else {
+                right = mid-1;
+            }
+        }
+        return result;
+    }
+
+    private static int lowerBound(int head) {
+        int left = head+1;
+        int right = N-2;
+        int result = -1;
+
+        while (left <= right) {
+            int mid = left + (right-left)/2;
+
+            if ((sum[N-1]-sum[mid]) < (sum[mid]-sum[head])) {
+                result = mid;
+                right = mid-1;
+            } else {
+                left = mid+1;
+            }
+        }
+        return result;
+    }
+}
+```