【数论】【扩展欧几里得】Codeforces 710D Two Arithmetic Progressions

 1 //
 2 //by coolxxx
 3 //#include<bits/stdc++.h>
 4 #include<iostream>
 5 #include<algorithm>
 6 #include<string>
 7 #include<iomanip>
 8 #include<map>
 9 #include<memory.h>
10 #include<time.h>
11 #include<stdio.h>
12 #include<stdlib.h>
13 #include<string.h>
14 //#include<stdbool.h>
15 #include<math.h>
16 #define min(a,b) ((a)<(b)?(a):(b))
17 #define max(a,b) ((a)>(b)?(a):(b))
18 #define abs(a) ((a)>0?(a):(-(a)))
19 #define lowbit(a) (a&(-a))
20 #define sqr(a) ((a)*(a))
21 #define swap(a,b) ((a)^=(b),(b)^=(a),(a)^=(b))
22 #define mem(a,b) memset(a,b,sizeof(a))
23 #define eps (1e-8)
24 #define J 10
25 #define mod 1000000007
26 #define MAX 0x7f7f7f7f
27 #define PI 3.14159265358979323
28 #define N 20000004
29 using namespace std;
30 typedef long long LL;
31 int cas,cass;
32 int n,m,lll,ans;
33 LL a1,a2,b1,b2,l,r;
34 LL exgcd(LL a,LL b,LL &x,LL &y)
35 {
36     if(!b){x=1,y=0;return a;}
37     LL d=exgcd(b,a%b,y,x);
38     y-=a/b*x;
39     return d;
40 }
41 int main()
42 {
43     #ifndef ONLINE_JUDGE
44 //    freopen("1.txt","r",stdin);
45 //    freopen("2.txt","w",stdout);
46     #endif
47     int i,j,k;
48     LL a,b,c,d,x,y,ny,lcm;
49 //    for(scanf("%d",&cas);cas;cas--)
50 //    for(scanf("%d",&cas),cass=1;cass<=cas;cass++)
51 //    while(~scanf("%s",s+1))
52     while(~scanf("%I64d",&a1))
53     {
54         cin>>b1>>a2>>b2>>l>>r;
55         l=max(l,b1);l=max(l,b2);
56         d=exgcd(a1,a2,x,y);
57         lcm=a1/d*a2;
58         if((b2-b1)%d!=0)
59         {
60             puts("0");
61             continue;
62         }
63         a=a1/d;b=a2/d;c=(b2-b1)/d;
64         d=exgcd(a,b,x,y);
65         x=a1*(x*c)+b1;
66         if(x>l)x=x-(x-l)/lcm*lcm;
67         else x=x+(l-1-x+lcm)/lcm*lcm;
68         if(x>r)puts("0");
69         else printf("%I64d\n",(r-x+lcm)/lcm-(l-1-x+lcm)/lcm);
70     }
71     return 0;
72 }
73 /*
74 //
75 
76 //
77 */