C语言程序 判断P1和P2位于这条直线的同一边，输出YES，否则输出NO 提交为WA

Question

#include
int main()
{
int x1,x2,y1,y2;
int a,b,c;
int x3,x4,y3,y4,c1,c2;
scanf("%d%d%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);

a=y2-y1;
b=x1-x2;
c=x1*y2-y1*x2;
c1=a*x3+b*y3;
c2=a*x4+b*y4;

if(c1>=c && c2>=c)

    printf("YES");
else if(c1<c && c2<c)
    printf("YES");
else 
    printf("NO");

return 0;

}

Answer 1

#include
int main()
{
int x1,x2,y1,y2;
int a,b,c;
int x3,x4,y3,y4,c1,c2;
scanf("%d%d%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);

a=y2-y1;
b=x1-x2;
c=x1*y2-y1*x2;
c1=a*x3+b*y3;
c2=a*x4+b*y4;

if(c1>c && c2>c)
printf("YES");
else if(c1<c && c2<c)
printf("YES");
else
printf("NO");
return 0;
}
应该没有错，你那个也可怡运行吧，哪里错你都没有描述