欧几里得: int gcd(int a,int b) { if(!b) return a; while((a%=b) && (b%=a)); return a+b; } 扩展欧几里得: int exgcd(int a, int b, int &x, int &y) { int x1 = 1, x2 = 0, x3 = 0, x4 = 1; while (b != 0) { int c = a / b; tie(x1, x2, x3, x4, a, b) = make_tuple(x3, x4, x1 - x3 * c, x2 - x4 * c, b, a - b...