From 7f8ac89ee50772944bd2ed760ae67f8d10191849 Mon Sep 17 00:00:00 2001
From: "YeJun, Jung" <yejun614@naver.com>
Date: Mon, 20 Apr 2026 08:54:39 +0900
Subject: [PATCH] feat: add swea p4038 solution

---
 problems/SWEA/p4038/Solution.java | 119 ++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 problems/SWEA/p4038/Solution.java

diff --git a/problems/SWEA/p4038/Solution.java b/problems/SWEA/p4038/Solution.java
new file mode 100644
index 0000000..7a150c0
--- /dev/null
+++ b/problems/SWEA/p4038/Solution.java
@@ -0,0 +1,119 @@
+/*
+ * (4038) [Professional] 단어가 등장하는 횟수
+ * https://swexpertacademy.com/main/code/problem/problemDetail.do?contestProbId=AWIoEJzarUwDFAWN&categoryId=AWIoEJzarUwDFAWN&categoryType=CODE&problemTitle=4038&orderBy=FIRST_REG_DATETIME&selectCodeLang=ALL&select-1=&pageSize=10&pageIndex=1
+ */
+
+import java.io.*;
+import java.util.*;
+
+/**
+ * SW Expert Academy - [Professional] 단어가 등장하는 횟수
+ * @author YeJun, Jung
+ * 
+ * [분석]
+ *   - 책의 내용에서 특정 단어가 몇 번 등장하는지 카운트해야 한다.
+ * 
+ * [전략]
+ *   - 2중 반복문은 시간복잡도가 높기 때문에 전략적으로 KMP 알고리즘을 사용해야 한다.
+ *   - makePi() 함수를 사용해서 찾고자 하는 단어의 prefix, postfix를 카운트해서 각 index에 저장한다.
+ *   - kmp 알고리즘을 사용해서 특정 단어가 몇 번 등장하는지 카운트한다.
+ */
+public class Solution {
+  static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+  static StringBuilder output = new StringBuilder();
+  static StringTokenizer input;
+
+  // ----------------------------------------------------------
+
+  public static void main(String[] args) throws IOException {
+    final int testCount = nextInt();
+
+    for (int testCase = 1; testCase <= testCount; testCase++) {
+      new Solution(testCase).run();
+    }
+
+    System.out.print(output.toString());
+  }
+
+  // ----------------------------------------------------------
+
+  int testCase;
+  int answer;
+
+  String book;
+  String target;
+  int bookLen;
+  int targetLen;
+
+  int[] pi;
+
+  public Solution(int testCase) { this.testCase = testCase; }
+  public void run() throws IOException { input(); solve(); print(); }
+
+  private void input() throws IOException {
+    book = next();
+    target = next();
+
+    bookLen = book.length();
+    targetLen = target.length();
+  }
+
+  private void solve() {
+    answer = 0;
+
+    makePi();
+    kmp();
+  }
+
+  private void makePi() {
+    pi = new int[targetLen];
+
+    for (int p0 = 0, p1 = 1; p1 < targetLen; p1++) {
+      while (p0 > 0 && target.charAt(p0) != target.charAt(p1)) {
+        p0 = pi[p0 - 1];
+      }
+
+      if (target.charAt(p0) == target.charAt(p1)) {
+        pi[p1] = ++p0;
+      }
+    }
+  }
+
+  private void kmp() {
+    for (int p0 = 0, p1 = 0; p0 < bookLen; p0++) {
+      while (p1 > 0 && book.charAt(p0) != target.charAt(p1)) {
+        p1 = pi[p1 - 1];
+      }
+
+      if (book.charAt(p0) == target.charAt(p1)) {
+        if (p1 == targetLen - 1) {
+          answer++;
+          p1 = pi[p1];
+        } else {
+          p1++;
+        }
+      }
+    }
+  }
+
+  private void print() {
+    output
+      .append('#')
+      .append(testCase)
+      .append(' ')
+      .append(answer)
+      .append('\n');
+  }
+
+  // ----------------------------------------------------------
+
+  static String next() throws IOException {
+    if (input == null || !input.hasMoreTokens())
+      input = new StringTokenizer(reader.readLine().trim());
+    return input.nextToken();
+  }
+
+  static int nextInt() throws IOException {
+    return Integer.parseInt(next());
+  }
+}