poj 1654 Area（计算几何--叉积求多边形面积）

  一个简单的用叉积求任意多边形面积的题,并不难,但我却错了很多次,double的数据应该是要转化为long long,我转成了int...这里为了节省内存尽量不开数组,直接计算,我MLE了一发...,最后看了下别人的才过,我的代码就不发了,免得误导,不得不说几何真是...

还有就是这个大神的代码,貌似G++,过不了,C++AC

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <iostream>
using namespace std;
int moveY[20] = {-1, 0, 1, -1, 0, 1, -1, 0, 1};
int moveX[20] = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
char step[1000007];
#define EPS 1e-8
int main()
{
    int t;
    scanf("%d
", &t);
    int x, y, px, py;
    double area;
    long pos = 0;
    while (t--)
    {
        x = y = px = py = 0;
        pos = area = 0;
        scanf("%s", step);
        while (step[pos] != '5')
        {
            x = px + moveX[step[pos]-'1'];
            y = py + moveY[step[pos]-'1'];
            area += 0.5*(px*y-py*x);
            px = x;
            py = y;
            pos++;
        }
        area = fabs(area);
        if (fabs((long long)area - area)<EPS)
        {
            printf("%.0lf
", area);
        }
        else
        {
            printf("%.1lf
", area);
        }
    }
    return 0;
}