myknn.cpp

#include <cstdlib>
#include <algorithm>
#include <numeric>
#include <vector>
#include <stdio.h>
#include <iostream>
#include <map>
#include <cmath>
#include <math.h>

std::vector<int> argsort(double* input_list, int length) {
    std::vector<int> out(length);
    iota(out.begin(), out.end(), 0);
    sort(out.begin(), out.end(),
       [&input_list](int i1, int i2) {return input_list[i1] < input_list[i2];});
    std::vector <int> v2(out.begin()+1 , out.end());
    return v2;
}

double edist(double* arr1, double* arr2, int n) {
    double sum = 0.0;
    for (int i=0; i<n; i++) {
        sum += pow(arr1[i] - arr2[i], 2);
    }
    return sqrt(sum); 
}

std::map<int, std::vector<int> > distance_knn(const double *array,int N, int M) {
     std::map<int, std::vector<int> > dist;
    double **arr = new double*[N];
    for (int i = 0; i < N; i++) {
        arr[i] = new double[M];
        for(int j=0; j < M; j++) {
            arr[i][j] = array[i*M+j];
        }
    }
     for (int i=0; i<N; i++) {
        double distances[N];
        for(int j=0; j<N; j++) {
            // distances.push_back();
            distances[j] = edist(arr[i], arr[j], M);
        }
        dist[i] = argsort(distances, N);
    }
    return dist;
}