SGU 136 高斯消元法的特殊情况

#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<set>
#include<cmath>
#include<cassert>
#include<cstring>
#include<iomanip>
using namespace std;

/*---------------for topcoder----------------------------------*/

#ifdef _WIN32
#define i64 __int64
#define out64 "%I64d\n"
#define in64 "%I64d"
#else
#define i64 long long
#define out64 "%lld\n"
#define in64 "%lld"
#endif

#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)
#define FF(i,a)         for( int i = 0 ; i < (a) ; i ++)
#define FFD(i,a)        for( int i = (a)-1 ; i >= 0 ; i --)
#define S64(a)          scanf(in64,&a)
#define SS(a)           scanf("%d",&a)
#define LL(a)           ((a)<<1)
#define RR(a)           (((a)<<1)+1)
#define SZ(a)           ((int)a.size())
#define PP(n,m,a)       puts("---");FF(i,n){FF(j,m)cout << a[i][j] << ' ';puts("");}
#define pb              push_back
#define CL(Q)           while(!Q.empty())Q.pop()
#define MM(name,what)   memset(name,what,sizeof(name))
#define read            freopen("in.txt","r",stdin)
#define write           freopen("out.txt","w",stdout)

const int inf = 0x3f3f3f3f;
const i64 inf64 = 0x3f3f3f3f3f3f3f3fLL;
const double oo = 10e9;
const double eps = 10e-6;
const double pi = acos(-1.0);

i64 gcd(i64 _a, i64 _b)
{
    if (!_a || !_b)
    {
        return max(_a, _b);
    }
    i64 _t;
    while (_t = _a % _b)
    {
        _a = _b;
        _b = _t;
    }
    return _b;
};

i64 ext_gcd (i64 _a, i64 _b, i64 &_x, i64 &_y)
{
    if (!_b)
    {
        _x = 1;
        _y = 0;
        return _a;
    }
    i64 _d = ext_gcd (_b, _a % _b, _x, _y);
    i64 _t = _x;
    _x = _y;
    _y = _t - _a / _b * _y;
    return _d;
}

i64 invmod (i64 _a, i64 _p)
{
    i64 _ans, _y;
    ext_gcd (_a, _p, _ans, _y);
    _ans < 0 ? _ans += _p : 0;
    return _ans;
}

/*---------------------------------------------------------------*/

const int maxn = 10011;

double x[maxn];
double y[maxn];
double mx[maxn];
double my[maxn];

int n;

int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
    {
     //   scanf("%d %d",&mx[i],&my[i]);
        cin>>mx[i]>>my[i];
        mx[i]*=2.0;
        my[i]*=2.0;
    }
    double tempx=0;
    double tempy=0;
    for(int i=n;i>=1;i--)
    {
        tempx = -tempx + mx[i];
        tempy = -tempy + my[i];
    }
    double tx = tempx;
    double ty = tempy;
    if(n%2)
    {
        x[1] = tx/2.0;
        y[1] = ty/2.0;
        for(int i=1;i<=n-1;i++)
        {
            x[i+1] = mx[i] - x[i];
            y[i+1] = my[i] - y[i];
        }
        cout<<"YES"<<endl;
        for(int i=1;i<=n;i++)
        {
            printf("%.3lf",x[i]);
            printf(" ");
            printf("%.3lf\n",y[i]);
        }
    }
    else
    {
        if(tempx < eps && tempx > - eps && tempy < eps && tempy > -eps)
        {
            x[1] = 0.0;
            y[1] = 0.0;
            for(int i=1;i<=n-1;i++)
            {
                x[i+1] = mx[i]-x[i];
                y[i+1] = my[i]-y[i];
            }
            cout<<"YES"<<endl;
            for(int i=1;i<=n;i++)
            {
                printf("%.3lf",x[i]);
                printf(" ");
                printf("%.3lf\n",y[i]);
            }
        }
        else
        {
            cout<<"NO"<<endl;
        }
    }

  //  system("pause");
    return 0;
}