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Makefile and heap in merge file #4

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Makefile and heap in merge file #4

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b8d43ee
Todo: heap in merge files
lelandfy Jun 1, 2014
141cac1
a simple makefile, will be revised
lelandfy Jun 2, 2014
48af508
add heap in do_file_merge
lelandfy Jun 5, 2014
da97c87
minor fix of heap
lelandfy Jun 5, 2014
e0487f1
minor fix
lelandfy Jun 5, 2014
670ffda
indent change
lelandfy Jun 5, 2014
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2 changes: 2 additions & 0 deletions examples/friends/Makefile
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
all:
g++ -Wall -std=c++11 -I../../include -I/usr/include/boost friends.cpp -o friends -lboost_system -lboost_filesystem -lboost_iostreams -pthread
11 changes: 9 additions & 2 deletions include/detail/mergesort.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include <sstream>
#include <fstream>
#include <iostream>
#include <algorithm>
#include <boost/filesystem.hpp>

#ifdef __GNUC__
Expand Down Expand Up @@ -49,7 +50,7 @@ bool const do_file_merge(It first, It last, std::string const &outfilename)
// in the meantime, we assert if we go round the loop more than once as it will produce incorrect results
assert(++count == 1);

typedef std::list<std::pair<std::shared_ptr<std::ifstream>, std::string> > file_lines_t;
typedef std::vector<std::pair<std::shared_ptr<std::ifstream>, std::string> > file_lines_t;
file_lines_t file_lines;
for (; first!=last; ++first)
{
Expand All @@ -66,18 +67,24 @@ bool const do_file_merge(It first, It last, std::string const &outfilename)
file_lines.push_back(std::make_pair(file, line));
}

std::make_heap(begin(file_lines), end(file_lines), [](const std::string& l, const std::string& r) { return l > r; });
while (file_lines.size() > 0)
{
typename file_lines_t::iterator it;
if (file_lines.size() == 1)
it = file_lines.begin();
else
it = std::min_element(file_lines.begin(), file_lines.end());
{
std::pop_heap(begin(file_lines), end(file_lines));
it = file_lines.back();
}
outfile << it->second << "\r";

std::getline(*it->first, it->second, '\r');
if (it->first->eof())
file_lines.erase(it);
else
std::push_heap(begin(file_lines), end(file_lines));
}
}

Expand Down