POJ 2954 Triangle (Pick定理）

题意：输入三角形的三个顶点。求三角形内部说包含的点的个数。

#include<cstdio>#include<cmath>#include<cstdlib>#include<algorithm>using std::swap;int gcd ( int x, int y ){    int tmp;    if ( x < y ) swap(x,y);    while ( y ) { tmp = y; y = x % y; x = tmp; }    return x;}int main(){    int x1, y1, x2, y2, x3, y3;    while ( 1 )    {        scanf("%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3);        if ( !x1 && !y1 && !x2 && !y2 && !x3 && !y3 ) break;        double s =fabs((x1-x3)*(y2-y3)-(x2-x3)*(y1-y3)+0.0) / 2.0;        int dx1 = abs(x1-x2), dy1 = abs(y1-y2);        int dx2 = abs(x2-x3), dy2 = abs(y2-y3);        int dx3 = abs(x3-x1), dy3 = abs(y3-y1);        int b = gcd ( dx1, dy1 ) + gcd ( dx2, dy2 ) + gcd(dx3,dy3);        int i = (int)(s)- b / 2 + 1;        printf("%d\n",i);    }    return 0;}