给你两个格点，求以它们为端点的线段上有多少个格点

答案为gcd(abs(x1-x2), abs(y1-y2)) + 1

1 #include 
     
       2 #include 
      
        3 #include 
       
         4 #include 
        
          5 #define INF 0x3f3f3f3f 6 using namespace std; 7 typedef long long LL; 8  9 int T;10 LL x1, y1, x2, y2;11 12 LL gcd(LL a, LL b) {13     return b == 0 ? a : gcd(b, a % b);14 }15 16 int main() {17     scanf("%d", &T);18     for (int t = 1; t <= T; t++) {19         scanf("%lld%lld%lld%lld", &x1, &y1, &x2, &y2);20         printf("Case %d: %lld\n", t, 1 + gcd(abs(x1 - x2), abs(y1 - y2)));21     }22     return 0;23 }