NO10——各种欧几里得

 int gcd(int n,int m)//n>m
 {
     //最大公约数
     int r;
     while(m)
     {
         r = n%m;
         n = m;
         m = r;
     }
     return n;
 }

 int kgcd(int a,int b)
 {
     if(!a) return b;
     if(!b) return a;
     if(!(a&) && !(b&))
         return kgcd(a>>,b>>)<<;
     else if(!(b&)) return kgcd(a,b>>);
     else if(!(a&)) return kgcd(a>>,b);
     else return kgcd(abs(a-b),min(a,b));
 }

 //扩展欧几里得
 //求方程ax+by+c = 0有多少整数解
 int extgcd(int a,int b,int &x,int &y)
 {
     if(!b)
     {
         x=;
         y=;
         return a;
     }
     int d = extgcd(b,a%b,x,y);
     int t = x;
     x=y;
     y=t-a/b*y;
     return d;
 }