HOJ 2089 4th point

http://acm.hit.edu.cn/hoj/problem/view?id=2089

给出平行四边形的三个点 寻找第四个

给出的三个点有一个重复

找出重复点 利用对角线交点坐标求第四个

#include <stdio.h>int main(){    int i, j;    double x[5], y[5], x4, y4;        while (scanf("%lf %lf %lf %lf %lf %lf %lf %lf", &x[0], &y[0], &x[1], &y[1], &x[2], &y[2], &x[3], &y[3]) != EOF)    {        for (i = 0; i < 2; i++)        {            for (j = 2; j < 4; j++)            {                if ( (x[i] == x[j]) && (y[i] == y[j]) )                {                    x[4] = x[i],y[4] = y[i];                    break;                }            }        }        x4 = x[0] + x[1] + x[2] + x[3] - 3 * x[4];        y4 = y[0] + y[1] + y[2] + y[3] - 3 * y[4];        printf("%.3lf %.3lf\n", x4, y4);    }    return 0;}