[20250214] BOJ / 골드2 / 벡터 매칭 / 이강현

lkhyun/202502/14 BOJ 골드2 벡터 매칭.md

@@ -0,0 +1,57 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static int N, half;
+    static int[] x;
+    static int[] y;
+    static long totalX, totalY;
+    static double best;
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int T = Integer.parseInt(br.readLine());
+
+        StringBuilder sb = new StringBuilder();
+        for (int t = 0; t < T; t++) {
+            N = Integer.parseInt(br.readLine());
+            half = N / 2;
+            x = new int[N];
+            y = new int[N];
+            totalX = 0;
+            totalY = 0;
+
+            for (int i = 0; i < N; i++) {
+                StringTokenizer st = new StringTokenizer(br.readLine());
+                x[i] = Integer.parseInt(st.nextToken());
+                y[i] = Integer.parseInt(st.nextToken());
+                totalX += x[i];
+                totalY += y[i];
+            }
+
+            best = Double.MAX_VALUE;
+            dfs(0, 0, 0, 0);
+            sb.append(String.format("%f\n", best));
+        }
+        System.out.print(sb);
+    }
+    static void dfs(int index, int count, long curX, long curY) {
+        if (count == half) {
+            // 선택한 점들의 합으로부터 최종 벡터 합 계산: 2*(cur) - (total)
+            long diffX = 2 * curX - totalX;
+            long diffY = 2 * curY - totalY;
+            double length = Math.sqrt(diffX * diffX + diffY * diffY);
+            best = Math.min(best, length);
+            return;
+        }
+
+        if (index >= N || (N - index) < (half - count))//범위를 넘거나 선택해야 하는 점 개수만큼 남아있지 않을때
+            return;
+
+        dfs(index + 1, count + 1, curX + x[index], curY + y[index]);// 현재 점 선택
+        dfs(index + 1, count, curX, curY);// 현재 점 선택x
+    }
+}
+
+```