DFT

#include "stdafx.h"//vs2010

#include <iostream>
#include <complex>
#include <cassert>
#include <vector>
#include <conio.h>
#include <windows.h>
#include "decimal.h"
#include "gnuplot_i.hpp"

using namespace std;
using namespace dec;

#define M_PI 3.14159265358979323846
#define dec10 decimal<10>
#define dabs(a) fabs((a).getAsDouble())
#define FOUT
#define cyrillic setlocale(LC_CTYPE, "rus")

inline string dtos(double d){ostringstream strs; strs << d; return strs.str();}

void wait(){
    FlushConsoleInputBuffer(GetStdHandle(STD_INPUT_HANDLE));
    #ifndef FOUT
        cout << endl << "Press any key to continue..." << endl;
    #endif
    _getch();
}

int main(){
    cyrillic;
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);

    vector<dec10> x;
    dec10 tmp;

    while(cin >> tmp){
        x.push_back(tmp);
    }

    int n = x.size();

    vector<dec10> dft(n + 1);

    for(int i = 0 ; i < n ; ++i){
        dec10 real = dec10(0);
        for(int j = 0 ; j < n ; ++j){
            dec10 angle = dec10((2 * M_PI * i * j) / n);
            real += x[j] * dec10(cos(angle.getAsDouble()));
        }
        dft[i] = real;
    }

    vector<pair<dec10 , dec10>> mx; //{coordinate , value}

    for(int i = 0 ; i < n / 2 ; ++i){
        if(!i){
            if(dft[i] > dft[i + 1]){
                mx.push_back(make_pair(i * 0.01 , dft[i]));
            }
        }else{
            if(dft[i] > dft[i + 1] && dft[i] > dft[i - 1]){
                mx.push_back(make_pair(i * 0.01 , dft[i]));
            }
        }
    }

    for(int i = 0 ; i < mx.size() ; ++i){
        cout << mx[i].second << " ";
    }

    reverse(dft.begin() , dft.end());
    dft.pop_back();
    reverse(dft.begin() , dft.end());

    string to_plot = "[0:5] ";
    int cur = 0;

    for(double i = 0. ; fabs(i - 5.00) > 1e-3 ; i += 0.01){
        if(fabs(i - 4.99) <= 1e-3){
            to_plot += dtos(dabs(dft[cur]));
            break;
        }
        to_plot += "x>=";
        to_plot += dtos(i);
        to_plot += "&x<";
        to_plot += dtos(i + 0.01);
        to_plot += "?";
        to_plot += dtos(dabs(dft[cur++]));
        to_plot += ":";
    }

    Gnuplot gnu("lines");

    gnu.plot_equation(to_plot,"dft");

    wait();

    return 0;
}