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[Silver III] Title: 썸 팰린드롬, Time: 104 ms, Memory: 14352 KB -BaekjoonHub
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‎백준/Silver/25180. 썸 팰린드롬/README.md‎

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# [Silver III] 썸 팰린드롬 - 25180
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[문제 링크](https://www.acmicpc.net/problem/25180)
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### 성능 요약
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메모리: 14352 KB, 시간: 104 ms
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### 분류
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수학, 그리디 알고리즘
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### 제출 일자
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2026년 2월 25일 23:28:50
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### 문제 설명
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<p>재혁이는 최근에 두람이와 썸을 타기 시작했다. 어느 날 재혁이가 귀찮아진 두람이는 재혁이에게 말했다.</p>
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<blockquote>
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<p> "내가 정수 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mi class="mjx-i"><mjx-c class="mjx-c1D441 TEX-I"></mjx-c></mjx-mi></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$N$</span></mjx-container>을 줄 테니 각 자릿수의 <strong>합(sum)</strong>이 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mi class="mjx-i"><mjx-c class="mjx-c1D441 TEX-I"></mjx-c></mjx-mi></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$N$</span></mjx-container>이 되는 썸 팰린드롬 수의 최소 자릿수를 구하면 썸 타줄게"</p>
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</blockquote>
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<p>팰린드롬 수는 앞으로 읽어도, 뒤로 읽어도 같은 수이다. 예를 들어 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c31"></mjx-c><mjx-c class="mjx-c32"></mjx-c><mjx-c class="mjx-c33"></mjx-c><mjx-c class="mjx-c31"></mjx-c></mjx-mn></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>1231</mn></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$1231$</span></mjx-container>은 팰린드롬 수가 아니고, <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c32"></mjx-c><mjx-c class="mjx-c31"></mjx-c><mjx-c class="mjx-c31"></mjx-c><mjx-c class="mjx-c32"></mjx-c></mjx-mn></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2112</mn></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$2112$</span></mjx-container>는 앞으로 읽어도, 뒤로 읽어도 같은 수이기 때문에 팰린드롬 수이다.</p>
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<p>썸 팰린드롬 수는 팰린드롬 수의 조건을 만족하면서 각 자리 숫자의 합이 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mi class="mjx-i"><mjx-c class="mjx-c1D441 TEX-I"></mjx-c></mjx-mi></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$N$</span></mjx-container>이 되는 수이다.</p>
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<p>예를 들어 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mi class="mjx-i"><mjx-c class="mjx-c1D441 TEX-I"></mjx-c></mjx-mi></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$N$</span></mjx-container>이 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c31"></mjx-c><mjx-c class="mjx-c35"></mjx-c></mjx-mn></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>15</mn></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$15$</span></mjx-container>라면 재혁이가 만들 수 있는 썸 팰린드롬 수는 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c34"></mjx-c><mjx-c class="mjx-c32"></mjx-c><mjx-c class="mjx-c33"></mjx-c><mjx-c class="mjx-c32"></mjx-c><mjx-c class="mjx-c34"></mjx-c></mjx-mn></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>42324</mn></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$42324$</span></mjx-container>가 있다. 하지만, <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c35"></mjx-c><mjx-c class="mjx-c35"></mjx-c><mjx-c class="mjx-c35"></mjx-c></mjx-mn></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>555</mn></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$555$</span></mjx-container>도 만들 수 있기 때문에 썸 팰린드롬의 최소 자릿수는 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c33"></mjx-c></mjx-mn></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>3</mn></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$3$</span></mjx-container>이다.</p>
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<p>외로운 재혁이를 도와주자. </p>
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### 입력
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<p>첫째 줄에 각 자리수의 합이 되는 정수 <mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mi class="mjx-i"><mjx-c class="mjx-c1D441 TEX-I"></mjx-c></mjx-mi></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$N$</span></mjx-container>(<mjx-container class="MathJax" jax="CHTML" style="font-size: 111.4%; position: relative;"><mjx-math class="MJX-TEX" aria-hidden="true"><mjx-mn class="mjx-n"><mjx-c class="mjx-c31"></mjx-c></mjx-mn><mjx-mo class="mjx-n" space="4"><mjx-c class="mjx-c2264"></mjx-c></mjx-mo><mjx-mi class="mjx-i" space="4"><mjx-c class="mjx-c1D441 TEX-I"></mjx-c></mjx-mi><mjx-mo class="mjx-n" space="4"><mjx-c class="mjx-c2264"></mjx-c></mjx-mo><mjx-msup space="4"><mjx-mn class="mjx-n"><mjx-c class="mjx-c31"></mjx-c><mjx-c class="mjx-c30"></mjx-c></mjx-mn><mjx-script style="vertical-align: 0.393em;"><mjx-mn class="mjx-n" size="s"><mjx-c class="mjx-c39"></mjx-c></mjx-mn></mjx-script></mjx-msup></mjx-math><mjx-assistive-mml unselectable="on" display="inline"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>1</mn><mo>≤</mo><mi>N</mi><mo>≤</mo><msup><mn>10</mn><mn>9</mn></msup></math></mjx-assistive-mml><span aria-hidden="true" class="no-mathjax mjx-copytext">$1 \le N \le 10^9$</span></mjx-container>)이 주어진다.</p>
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### 출력
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<p>첫째 줄에 재혁이가 만들 수 있는 팰린드롬 수의 최소 자릿수를 출력한다.</p>
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‎백준/Silver/25180. 썸 팰린드롬/썸 팰린드롬.java‎

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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.io.InputStreamReader;
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import java.util.*;
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public class Main {
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public static void main(String[] args) throws Exception {
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BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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// BufferedReader br = new BufferedReader(new FileReader("input.txt"));
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StringTokenizer st = new StringTokenizer(br.readLine());
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int n = Integer.parseInt(st.nextToken());
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// n = 15라면 한 자리(최대 값 9)로는 안되고 최소 2자리부터 시작
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int k = (int) Math.ceil((double) n / 9);
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while (true) {
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//k
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// 짝수 자릿수를 가지면, 홀수 N을 절대 만들 수 없음
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if (k % 2 == 0 && n % 2 != 0) {
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k++;
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} else {
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System.out.println(k);
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break;
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}
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}
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br.close();
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}
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}

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