[20251129] BOJ / G3 / 합이 0인 네 정수

Ukj0ng/202511/29 BOJ G3 합이 0인 네 정수.md

@@ -0,0 +1,96 @@
+```
+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[] A, B, C, D, AB, CD;
+    private static int n;
+    private static long answer;
+
+    public static void main(String[] args) throws IOException {
+        init();
+        for (int i = 0; i < n*n; i++) {
+            int min = binarySearch1(AB[i]);
+            int max = binarySearch2(AB[i]);
+
+            if (min == -1) continue;
+            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());
+
+        A = new int[n];
+        B = new int[n];
+        C = new int[n];
+        D = new int[n];
+        AB = new int[n*n];
+        CD = new int[n*n];
+
+        for (int i = 0; i < n; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            A[i] = Integer.parseInt(st.nextToken());
+            B[i] = Integer.parseInt(st.nextToken());
+            C[i] = Integer.parseInt(st.nextToken());
+            D[i] = Integer.parseInt(st.nextToken());
+        }
+
+        int index = 0;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                AB[index] = A[i]+B[j];
+                CD[index++] = C[i]+D[j];
+            }
+        }
+
+        Arrays.sort(AB);
+        Arrays.sort(CD);
+    }
+
+    private static int binarySearch1(int num) {
+        int left = 0;
+        int right = n*n-1;
+        int result = -1;
+
+        while (left <= right) {
+            int mid = left + (right-left)/2;
+
+            if (CD[mid] + num == 0) {
+                result = mid;
+                right = mid-1;
+            }
+            else if (CD[mid] + num > 0) right = mid-1;
+            else left = mid+1;
+        }
+
+        return result;
+    }
+
+    private static int binarySearch2(int num) {
+        int left = 0;
+        int right = n*n-1;
+        int result = -1;
+
+        while (left <= right) {
+            int mid = left + (right-left)/2;
+
+            if (CD[mid] + num == 0) {
+                result = mid;
+                left = mid+1;
+            }
+            else if (CD[mid] + num > 0) right = mid-1;
+            else left = mid+1;
+        }
+
+        return result;
+    }
+}
+```