HDOJ(HDU) 2504 又见GCD(利用最大公约数反推)

import java.util.Scanner;

public class Main{

public static void main(String[] args) {
Scanner sc= new Scanner(System.in);

int t =sc.nextInt();
while(t-->0){
int a =sc.nextInt();
int b =sc.nextInt();
int c=0;
for(int i=2;;i++){
if(goc(a,i*b,b)){
c=i*b;
break;
}
}
System.out.println(c);
}
}

//验证，a和c的最大公约数是不是b
private static boolean goc(int a, int c, int b) {
int n=a;
int m=c;
if(n<m){
n=n^m;
m=n^m;
n=n^m;
}

while(m>0){
int k=n%m;
n=m;
m=k;
}
if(n==b){
return true;
}
return false;
}
}