poj 1654(计算几何)(差乘运用)

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
using namespace std;
typedef long long LL;
const int N = 1000500;
char direction[][2] = { -1,-1,0,-1,1,-1,-1,0,0,0,1,0,-1,1,0,1,1,1 };
char dir
;
int polygon
[2];//储存坐标
int len;
LL Area_Triangle(int k,int d)
{
return polygon[k][0] * polygon[d][1] - polygon[k][1] * polygon[d][0];
}
LL Area()
{
LL s = 0;
for (int i = 0; i < len - 1; i++)
{
s += Area_Triangle(i, i + 1);
}
s += Area_Triangle(len - 1, 0);
if (s > 0)
return s;
else
return -1*s;
}
int main()
{
int t;
#ifdef glx
freopen("in.txt", "r", stdin);
#endif
scanf("%d", &t);
while (t--)
{
scanf("%s", dir);
len = strlen(dir);
polygon[0][0] = 0;
polygon[0][1] = 1;
for (int i = 1; i < len; i++)
{
int num = dir[i-1] - '1';
polygon[i][0] = polygon[i - 1][0] + direction[num][0];
polygon[i][1] = polygon[i - 1][1] + direction[num][1];
}
LL area = Area();
if (area % 2 == 0)
printf("%I64d\n", area / 2);
else printf("%I64d.5\n", area / 2);
}
return 0;
}