15758. 무한 문자열 JAVA

https://swexpertacademy.com/main/code/problem/problemDetail.do?problemLevel=3&contestProbId=AYP5JmsqcngDFATW&categoryId=AYP5JmsqcngDFATW&categoryType=CODE&problemTitle=&orderBy=FIRST_REG_DATETIME&selectCodeLang=JAVA&select-1=3&pageSize=10&pageIndex=1 

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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class SWEA12871 {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int test_case_cnt = Integer.parseInt(br.readLine());
		
		for (int i = 1; i <= test_case_cnt; i++) {
			StringTokenizer st = new StringTokenizer(br.readLine());
			
			String s = st.nextToken();
			String t = st.nextToken();
			
			String S = s;
			String T = t;
			
			int s_len = s.length();
			int t_len = t.length();
			
			if (s_len != t_len) {
				int lcm = lcm(s_len, t_len);
				while (S.length() != lcm) {
					S += s;
				}
				while (T.length() != lcm) {
					T += t;
				}	
			}
			
			if (S.equals(T)) {
				System.out.printf("#%d %s\n", i, "yes");
			} else {
				System.out.printf("#%d %s\n", i, "no");
			}
		}
	}
	
	// GCD 최대공약수
	public static int gcd(int a, int b) {
		if (b == 0) {
			return a;
		}
		
		return gcd(b, a % b);
		/*
		int r = 0;
		
		while( b != 0 ) {
			r = a % b;
			a = b;
			b = r;
		}
		
		return a;
		*/
	}
	
	// LCM 최소공배수
	public static int lcm(int a, int b) {
		return (a * b) / gcd(a, b);
	}
}