HDU2036 改革春风吹满地

给定n个点的坐标，求多边形面积：点击打开链接

#include <stdio.h>#include <string.h>struct Point {    int x, y;};intmain() {    struct Point p[105];    int n, i;    double area;    while (scanf("%d", &n) == 1 && n) {        memset(p, 0, sizeof(p));        for (i = 0; i < n; ++ i)            scanf("%d%d", &p[i].x, &p[i].y);        area = 0.0;        for (i = 1; i < n - 1; ++ i)            area += p[0].x*p[i+1].y + p[0].y*p[i].x + p[i+1].x*p[i].y - p[0].x*p[i].y -p[0].y*p[i+1].x -p[i+1].y*p[i].x;        area /= 2;        printf("%.1lf\n", -area);    }}