模板题_NOIp2012同余方程

题目链接：http://codevs.cn/problem/1200/

扩展gcd的模板题，代码如下

 1 #include<cstdio>

 2 #include<cstdlib>

 3 #include<cstring>

 4 #include<algorithm>

 5 using namespace std;

 6 #define lowbit(a) ((a)&(-a))

 7 #define max(a, b) ((a)>(b)?(a):(b))

 8 #define min(a, b) ((a)<(b)?(a):(b))

 9 #define MAXN 100010

10 #define PI 3.1415926

11 #define E 2.718281828

12 #define INF 0x777777f

13 typedef long long LL;

14 

15 inline int exGcd(int m,int n,int &x,int &y){

16     int x0=1,y0=0,x1=0,y1=1,r=m%n,q=(m-r)/n;x=0;y=1;

17     while(r){x=x0-q*x1;y=y0-q*y1;x0=x1;y0=y1;x1=x;y1=y;m=n;n=r;r=m%n;q=(m-r)/n;} return n;

18 }

19 int main(){

20     int a, b, x, y;

21     scanf("%d%d", &a, &b);

22     exGcd(a, b, x, y);

23     printf("%d", (x+b)%b);

24     return 0;

25 }