---
id: cpp-functions-recursion
title: "C++ Recursion"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["recursive function", "base case", "factorial recursion", "C++ 재귀"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.85
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["cpp", "programming-language", "w3schools", "functions", "recursion"]
raw_sources: ["https://www.w3schools.com/cpp/cpp_functions_recursion.asp"]
applied_in: []
github_commit: ""
---

# [[CPP Recursion]]

## 🎯 한 줄 통찰 (One-line insight)
The exact same three examples (range-sum via `sum(k)`, countdown, factorial) with the exact same step-by-step unfolding explanation reappear here verbatim from C's Recursion chapter — confirming C++'s recursion semantics, base-case requirement, and termination risks are inherited from C completely unmodified. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Recursion** — a function calling ITSELF, breaking a complex problem into smaller instances of the same problem. [S1]
- **Base case** — the condition under which the function stops calling itself (`k > 0` becoming false), essential for termination. [S1]
- **Unwinding accumulation** — each recursive call combines its own contribution with the result of the smaller sub-call. [S1]
- **Risk of non-termination or excess resource use** — without a solid base case, recursion can run forever or exhaust memory/processor time. [S1]

## 📖 세부 내용 (Details)
- Summing 1 to 10 via recursion: `int sum(int k) { if (k > 0) { return k + sum(k - 1); } else { return 0; } }` — unfolds as `10 + (9 + (8 + ... + sum(0)))`. [S1]
- Countdown via recursion: `void countdown(int n) { if (n > 0) { cout << n << " "; countdown(n - 1); } }`. [S1]
- Factorial via recursion: `int factorial(int n) { if (n > 1) { return n * factorial(n - 1); } else { return 1; } }` — factorial(5) = 120. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- 현재까지 발견된 모순 사항 없음 (No contradictions found in available sources). C 챕터와 완전히 동일한 재귀 예제와 설명이 확인됨.

## 🛠️ 적용 사례 (Applied in summary)
5의 팩토리얼(5×4×3×2×1=120)을 재귀로 계산하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

## 💻 코드 패턴 (Code patterns)
A recursive function with a clear base case that guarantees termination (C++):
```cpp
int factorial(int n) {
  if (n > 1) {
    return n * factorial(n - 1);
  } else {
    return 1; // base case
  }
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.85
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C++ Tutorial]]
- **관련 개념:** [[CPP Function Structures]], [[CPP Functions Lambda]], [[C Functions Recursion]]
- **참조 맥락:** 재귀 — 람다 함수(Functions Lambda) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C++ Recursion — https://www.w3schools.com/cpp/cpp_functions_recursion.asp

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "C++ Recursion" page (Astra wiki-curation, P-Reinforce v3.1 format).