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Heap.cpp
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Heap.cpp
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#include <RcppArmadillo.h>
#include <queue>
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::plugins(cpp11)]]
using namespace Rcpp;
using namespace std;
using arma::uword;
template <typename T>
arma::uvec top_i_heap(const arma::Col<T>& v, uword n) {
typedef pair<T, uword> pt_;
priority_queue<pt_, vector<pt_>, greater<pt_>> heap;
pt_ p;
for (uword i=0; i<v.size(); ++i) {
if (heap.size()<n)
heap.push(pt_(v[i], i));
else {
p = pt_(v[i], i);
if (heap.top() < p) {
heap.pop();
heap.push(p);
}
}
}
arma::uvec res(n);
for (uword i=0; i<n; ++i) {
res[i] = heap.top().second + 1;
heap.pop();
}
return res;
}
// [[Rcpp::export]]
arma::uvec top_index(SEXP x, uword n) {
switch(TYPEOF(x)) {
case INTSXP: return top_i_heap(as<arma::ivec>(x), n);
case REALSXP: return top_i_heap(as<arma::vec>(x), n);
case CPLXSXP: return top_i_heap(as<arma::cx_vec>(x), n);
// case STRSXP: return top_i_heap(as<arma::Col<string>>(x), n);
default: Rcpp::stop("unexpected data type");
}
return arma::uvec();
}