poj 1654 Area 求面积 水题 +longlong %lld输出

题目来源：
http://poj.org/problem?id=1654

代码如下：

typedef long long LL ;
const double EPS = 1e-10;
const int Max_N = 1000005;
char s[Max_N];
int dx[10]={0,-1,0,1,-1,0,1,-1,0,1};
int dy[10]={0,-1,-1,-1,0,0,0,1,1,1};
struct Point
{
    int x,y;
};
int xmult(Point p1, Point p2){
    return p1.x*p2.y-p1.y*p2.x;
}
Point p[Max_N];
LL sum;
int main(){

    int n;
    scanf("%d",&n);
    while(n--){

        scanf("%s",s);
        int len=strlen(s);
        if(len <3) {printf("0\n");continue;}
        p[0].x=0,p[0].y=0;
        for(int i=0; i<len; i++){
            p[i+1].x=p[i].x+dx[s[i]-'0' ];
            p[i+1].y=p[i].y+dy[s[i]-'0' ];
        }
        sum=0;
        for(int i=0; i<len; i++){
            sum+=xmult(p[i],p[i+1]);
        }
        if(sum<0) sum=-sum;

        if(sum & 1)
            printf("%lld.5\n",sum/2);
        else
            printf("%lld\n",sum/2);
    }
    return 0;
}