标签：
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 22698 Accepted Submission(s):
11741
#include<stdio.h>
int main()
{
int n,m,j,i,s;
double sum;
double a[110],b[110];
while(scanf("%d",&n),n)
{
for(i=0;i<n;i++)
{
scanf("%lf%lf",&a[i],&b[i]);
}
a[n]=a[0];b[n]=b[0];
sum=0;
for(i=1;i<=n;i++)
sum+=a[i-1]*b[i]-a[i]*b[i-1];
printf("%.1lf\n",sum/2);
}
return 0;
}
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原文地址：http://www.cnblogs.com/tonghao/p/4627713.html
