poj 2954 pick公式

poj 2954

S=a+b/2-1

#include <cstdio>
#include <cstdlib>
#define inf  0x7fffffff
#define linf 0x7fffffffffffffff
#define fil(x,y) memset(x,y,sizeof(x))
#define fup(i,x,y) for(int i=(x);i<=(y);i++)
#define fdn(i,x,y) for(int i=(x);i>=(y);i--)
#define sp(x) setprecision(x)
#define sd(n) scanf("%d",&n)
#define sdd(n,m) scanf("%d%d",&n,&m)
#define sddd(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define sld(n) scanf("%lld",&n)
#define sldd(n,m) scanf("%lld%lld",&n,&m)
#define slddd(n,m,k) scanf("%lld%lld%lld",&n,&m,&k)
#define sf(n) scanf("%lf",&n)
#define sff(n,m) scanf("%lf%lf",&n,&m)
#define sfff(n,m,k) scanf("%lf%lf%lf",&n,&m,&k)
#define sc(n) scanf("%s",n)
#define lowbit(x) (x&(-x))
#define pf(x) printf("%d\n",x)
#define pfl(x) printf("%lld\n",x)
#define pff(x) printf("%lf\n",x)
#define debug printf("!!\n");
#define N 1000005
#define M 4000009
#define pi acos(-1)
#define eps 1e-2
//cout.setf(ios::fixed);
//freopen("out.txt","w",stdout);// freopen("in.txt","r",stdin);
using namespace std;
typedef long long  ll;
typedef double db;
using namespace std;
typedef long long ll;
using namespace std;
struct node
{
    int x,y;
}a1,a2,a3;
int s(int x,int y,int x1,int y1)
{
    return abs(x*y1-y*x1);
}
int gcd(int x,int y)
{
    return y==0?x:gcd(y,x%y);
}
int po(int x,int y)
{
    if(x==0) return abs(y);
    if(y==0) return abs(x);
    return gcd(abs(x),abs(y));
}
int main()
{
    while(~sdd(a1.x,a1.y))
    {
        sdd(a2.x,a2.y);
        sdd(a3.x,a3.y);
        if(a1.x==0&&a2.x==0&&a3.x==0&&a1.y==0&&a2.y==0&&a3.y==0)break;
        int point=po(a2.x-a1.x,a2.y-a1.y)+po(a3.x-a2.x,a3.y-a2.y)+po(a3.x-a1.x,a3.y-a1.y);
        pf((s(a2.x-a1.x,a2.y-a1.y,a3.x-a1.x,a3.y-a1.y)+2-point)/2);
    }
    return 0;
}