Given two positive integers a and b,find suitable X and Y to meet the conditions:X+Y=a
Least Common Multiple (X, Y) =b
Input
Input includes multiple sets of test data.Each test data occupies one line,including two positive integers a(1≤a≤2*10^{4),b(1≤b≤10}9),and their meanings are shown in the description.Contains most of the 12W test cases.

如果存在x,y，則一定滿足 gcd(x,y) == gcd(a,b)，再根據題目，可以列出一元二次方程組，根據解求出x,y。

看了大佬題解才想出來的，

#include <bits/stdc++.h>
using namespace std;
int f(int x) {
    int a = sqrt(x);
    if (a * a == x) return 1;
    return 0;
}
int main() {
    int a, b, c, d, x, y;
    while (cin >> a >> b) {
        c = __gcd(a, b);
        a /= c;
        b /= c;
        d = a * a - 4 * b;
        if
 
 (d >= 0 && f(d)) {
            x = (a - sqrt(d)) / 2 * c;
            y = (a + sqrt(d)) / 2 * c;
            printf("%d %d\n", x, y);
        } else
            puts("No Solution");
    }
}