From ddbc3014722e8bbb58f4cfaba45772ba5f0bb359 Mon Sep 17 00:00:00 2001
From: SinnoLn <sintmtn69@gmail.com>
Date: Sat, 19 Sep 2026 18:06:46 +0900
Subject: [PATCH] 284. Peeking Iterator

---
 .../284. Peeking Iterator.java"               | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 "leetcode3/\354\235\264\354\247\204\355\235\254/284. Peeking Iterator.java"

diff --git "a/leetcode3/\354\235\264\354\247\204\355\235\254/284. Peeking Iterator.java" "b/leetcode3/\354\235\264\354\247\204\355\235\254/284. Peeking Iterator.java"
new file mode 100644
index 00000000..b46f4727
--- /dev/null
+++ "b/leetcode3/\354\235\264\354\247\204\355\235\254/284. Peeking Iterator.java"	
@@ -0,0 +1,43 @@
+/*
+
+1. 아이디어 : Iterator 구현체 메소드를 활용하여, peek()메소드 구현
+            공식 ref를 참고, peekVal 변수를 추가하고 미리 생성자 호출에서 next()를 진행해 다음값을 저장
+            이때 포인터까지 이동했으므로, next(), hasNext()모두 한 칸 앞선 포인터 기준으로 오버라이딩
+
+2. 시간복잡도 : O(N)
+
+3. 자료구조/알고리즘 : 구현
+
+ */
+
+// Java Iterator interface reference:
+// https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html
+
+class PeekingIterator implements Iterator<Integer> {
+    private Iterator<Integer> iter;
+    private int peekVal; 
+
+	public PeekingIterator(Iterator<Integer> iterator) {
+	    this.iter = iterator;
+        peekVal = iter.next();
+	}
+	
+	public Integer peek() {
+        return peekVal;
+	}
+	
+	@Override
+	public Integer next() {
+        int val = peekVal;
+        if(iter.hasNext()) peekVal = iter.next();
+        else peekVal = -1;
+	    
+        return val;
+	}
+	
+	@Override
+	public boolean hasNext() {
+	    if(peekVal == -1) return false;
+        return true;
+	}
+}
\ No newline at end of file