POJ 1654 Area 多边形面积

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#include<stdlib.h>
#define lld __int64
using namespace std;

struct point
{
lld x, y;
}p[1000003];

lld cal(int n, point *p)
{
int i;
lld s = 0;
p
= p[0];
for(i = 0; i < n; i++)
s +=  p[i].y * p[i+1].x - p[i].x * p[i+1].y;
return abs(s);
}

lld dir[10][2] = {0, 0, 1, -1, 0, -1, -1, -1, 1, 0, 0, 0, -1, 0, 1, 1, 0, 1, -1, 1};
char str[1000003];

int main()
{
int i, j, cas;
scanf("%d", &cas);
while( cas--)
{
p[0].x = 0; p[0].y = 0;
int num = 0;
scanf("%s", str);
char c;
int len = strlen(str);
for(i = 0; i < len; i++)
{
int k = str[i] - '0';
if(k == 5) break;
p[num+1].x = p[num].x + dir[k][0];
p[num+1].y = p[num].y + dir[k][1];
num++;
}
if(p[num].x == 0 && p[num].y == 0)
{
lld ans = cal(num, p);
if( ans & 1 ) printf("%I64d.5\n", ans/2);
else printf("%I64d\n", ans/2);
}
else printf("0\n");
}
return 0;
}