几何公式
两条直线是否相交
1 //叉积 2 double mult(Point a, Point b, Point c) 3 { 4 return (a.x-c.x)*(b.y-c.y)-(b.x-c.x)*(a.y-c.y); 5 } 6 7 //aa, bb为一条线段两端点 cc, dd为另一条线段的两端点 相交返回true, 不相交返回false 8 bool intersect(Point aa, Point bb, Point cc, Point dd) 9 { 10 if ( max(aa.x, bb.x)<min(cc.x, dd.x) ) 11 { 12 return false; 13 } 14 if ( max(aa.y, bb.y)<min(cc.y, dd.y) ) 15 { 16 return false; 17 } 18 if ( max(cc.x, dd.x)<min(aa.x, bb.x) ) 19 { 20 return false; 21 } 22 if ( max(cc.y, dd.y)<min(aa.y, bb.y) ) 23 { 24 return false; 25 } 26 if ( mult(cc, bb, aa)*mult(bb, dd, aa)<0 ) 27 { 28 return false; 29 } 30 if ( mult(aa, dd, cc)*mult(dd, bb, cc)<0 ) 31 { 32 return false; 33 } 34 return true; 35 }
圆周率计算代码
1 #include<stdio.h> 2 int main() 3 { 4 int n; 5 while(scanf("%d",&n)!=EOF&&n!=0) 6 { 7 int const N=7200; 8 int const M=10000; 9 int const B=10000; 10 int const L=4; 11 int s[M/L]; 12 int r1[N]= {0},r2[N]= {0},d1[N]= {0},d2; 13 int r3[N]= {0},r4[N]= {0},d3[N]= {0},d4; 14 int i,k,t,p=0,mp=M/L/20; 15 r1[0]=1; 16 r1[1]=3; 17 r3[0]=4; 18 printf("正在计算,请等待\n____________________\n"); 19 for(k=0; k<M/L; ++k) 20 { 21 t=r1[0]*B; 22 d1[0]=t/0x5; 23 r1[0]=t%0x5; 24 // 25 t=r3[0]*B; 26 d3[0]=t/0xEF; 27 r3[0]=t%0xEF; 28 s[k]=d1[0]-d3[0]; 29 int tag=0; 30 for(i=1; i<N; ++i) 31 { 32 t=r1[i]*B+d1[i-1]; 33 d1[i]=t/0x19; 34 r1[i]=t%0x19; 35 t=r2[i]*B+d1[i]; 36 d2=t/(2*i+1); 37 r2[i]=t%(2*i+1); 38 // 39 t=r3[i]*B+d3[i-1]; 40 d3[i]=t/0xDF21; 41 r3[i]=t%0xDF21; 42 t=r4[i]*B+d3[i]; 43 d4=t/(2*i+1); 44 r4[i]=t%(2*i+1); 45 if(tag) 46 { 47 s[k]+=(d2-d4); 48 tag=0; 49 } 50 else 51 { 52 s[k]+=(d4-d2); 53 tag=1; 54 } 55 } 56 if(p==mp) 57 { 58 printf(">"); 59 p=0; 60 } 61 else 62 p++; 63 } 64 for(i=M/L-1; i>=0; i--) 65 { 66 while(s[i]>=B) 67 { 68 s[i-1]++; 69 s[i]-=B; 70 } 71 while(s[i]<0) 72 { 73 s[i-1]--; 74 s[i]+=B; 75 } 76 } 77 printf("\npi=3.\n"); 78 for(i=0; i<M/L; ++i) 79 printf("%d",s[i]); 80 printf("\n"); 81 } 82 return 0; 83 84 }
求圆心
1 void count(double x1,double y1,double x2,double y2,double x3,double y3) 2 { 3 double a,b,c,d,e,f; 4 a=2*(x2-x1); 5 b=2*(y2-y1); 6 c=x2*x2+y2*y2-x1*x1-y1*y1; 7 d=2*(x3-x2); 8 e=2*(y3-y2); 9 f=x3*x3+y3*y3-x2*x2-y2*y2; 10 x=(b*f-e*c)/(b*d-e*a); 11 y=(d*c-a*f)/(b*d-e*a); 12 r=sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1)); 13 14 }
