One Person Game(zoj3593+扩展欧几里德)

 1 #include<stdio.h>
 2 #include<math.h>
 3 #include<algorithm>
 4 #define LL long long
 5 using namespace std;
 6 
 7 LL ans;
 8 void exgcd(LL a,LL b,LL& d,LL& x,LL& y)
 9 {
10     if(!b){d=a;x=1;y=0;}
11     else
12     {
13         exgcd(b,a%b,d,y,x);
14         y-=x*(a/b);
15     }
16 }
17 LL China(LL a,LL b,LL c)
18 {
19     LL x,y,d,bm,am;
20 
21     exgcd(a,b,d,x,y);
22     if(c%d) return -1;
23     bm=b/d;
24     am=a/d;
25     x=x*c/d;
26     y=y*c/d;
27 
28 
29     LL sum=fabs(x)+fabs(y);
30 
31     for(int i=-x/bm-1;i<=-x/bm+1;i++)
32     {
33         LL X=x+bm*i;
34         LL Y=y-am*i;
35         if(i)
36         {
37             LL tmp=fabs(X)+fabs(Y);
38             if(tmp<sum) sum=tmp;
39         }
40     }
41     for(int i=y/am-1;i<=y/am+1;i++)
42     {
43         LL X=x+bm*i;
44         LL Y=y-am*i;
45         if(i)
46         {
47             LL tmp=fabs(X)+fabs(Y);
48             if(tmp<sum) sum=tmp;
49         }
50     }
51     return sum;
52 }
53 
54 
55 int main()
56 {
57     int T;
58     LL A,B,C,a,b,c,d,x,y;
59     scanf("%d",&T);
60     while(T--)
61     {
62         scanf("%lld%lld%lld%lld",&A,&B,&a,&b);
63         c=a+b;
64         C=fabs(A-B);
65 
66         LL t1=China(a,b,C);
67         LL t2=China(a,c,C);
68         LL t3=China(b,c,C);
69 
70         if(t1==-1&&t2==-1&&t3==-1)
71         {
72             printf("-1\n");
73             continue;
74         }
75         if(t1>t2) ans=t2;
76         else ans=t1;
77 
78         if(ans>t3) ans=t3;
79 
80         printf("%lld\n",ans);
81     }
82     return 0;
83 }