Merge pull request #1003 from AlgorithmWithGod/Ukj0ng

[20250929] BOJ / G5 / 포스택 / 한종욱

Author: ShinHeeEul

Ukj0ng/202509/29 BOJ G5 포스택.md

@@ -0,0 +1,60 @@
+```
+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 Stack<Integer>[] stacks;
+    private static int N;
+
+    public static void main(String[] args) throws IOException {
+        init();
+
+        int answer = 0;
+        for (int i = 0; i < 4; i++) {
+            answer += stacks[i].size();
+        }
+
+        if (answer-4 == N) bw.write("YES");
+        else bw.write("NO");
+
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        stacks = new Stack[4];
+
+        for (int i = 0; i < 4; i++) {
+            stacks[i] = new Stack<>();
+            stacks[i].push(0);
+        }
+
+        N = Integer.parseInt(br.readLine());
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        for (int i = 0; i < N; i++) {
+            int num = Integer.parseInt(st.nextToken());
+            int min = N;
+            int index = -1;
+
+            for (int j = 0; j < 4; j++) {
+                if (stacks[j].peek() == 0) {
+                    index = j;
+                    continue;
+                }
+                int temp = num - stacks[j].peek();
+                if (temp < 0) continue;
+                if (temp < min) {
+                    index = j;
+                    min = temp;
+                }
+            }
+
+            if (index > -1) stacks[index].push(num);
+        }
+    }
+}
+```