Merge pull request #1034 from AlgorithmWithGod/LiiNi-coder

[20251003] BOJ / G5 / 블랙 프라이데이 / 이인희

Author: ShinHeeEul

LiiNi-coder/202510/03 BOJ 블랙 프라이데이.md

@@ -0,0 +1,70 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        int N = Integer.parseInt(st.nextToken());
+        int C = Integer.parseInt(st.nextToken());
+        int[] arr = new int[N];
+        st = new StringTokenizer(br.readLine());
+        for (int i = 0; i < N; i++) {
+            arr[i] = Integer.parseInt(st.nextToken());
+        }
+
+        Arrays.sort(arr);
+
+        //1개 확인
+        for(int i = 0; i < N; i++){
+            if (arr[i] == C) {
+                System.out.println(1);
+                return;
+            }
+        }
+
+        //2개 확인(투포인터 사용)
+        int l = 0, r = N - 1;
+        while(l < r){
+            int sum = arr[l] + arr[r];
+            if(sum == C){
+                System.out.println(1);
+                return;
+            }
+            if(sum < C)
+                l++;
+            else
+                r--;
+        }
+
+        //3개 확인(중간값 정하고 나머지값 투포인터로 찾기)
+        for(int i = 0; i < N; i++){
+            int target = C - arr[i];
+            int left = 0, right = N - 1;
+            while(left < right){
+                if(left == i){
+                    left++;
+                    continue;
+                }
+                if(right == i){
+                    right--;
+                    continue;
+                }
+                int sum = arr[left] + arr[right];
+                if(sum == target){
+                    System.out.println(1);
+                    return;
+                }
+                if(sum < target)
+                    left++;
+                else
+                    right--;
+            }
+        }
+
+        System.out.println(0);
+    }
+}
+
+```