std::greater by first (tools/greater_by_first.hpp)

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• Last update: 2021-03-29 00:30:01+09:00
• Include: #include "tools/greater_by_first.hpp"

It compares two pairs by the first element.

Usage

std::vector<std::pair<int, int>> a;
std::sort(a.begin(), a.end(), tools::greater_by_first());

License

• CC0

Author

• anqooqie

Constructor

tools::greater_by_first comp();

It creates a comparator.

Constraints

• None

Time Complexity

• $O(1)$

operator()

template <typename T1, typename T2>
bool comp(std::pair<T1, T2> x, std::pair<T1, T2> y);

It returns true if x.first > y.first. Otherwise, it returns false.

Constraints

• None

Time Complexity

• $O(1)$

Code

#ifndef TOOLS_GREATER_BY_FIRST_HPP
#define TOOLS_GREATER_BY_FIRST_HPP

#include <utility>

namespace tools {

  class greater_by_first {
  public:
    template <class T1, class T2>
    bool operator()(const ::std::pair<T1, T2>& x, const ::std::pair<T1, T2>& y) const {
      return x.first > y.first;
    }
  };
}

#endif

#line 1 "tools/greater_by_first.hpp"



#include <utility>

namespace tools {

  class greater_by_first {
  public:
    template <class T1, class T2>
    bool operator()(const ::std::pair<T1, T2>& x, const ::std::pair<T1, T2>& y) const {
      return x.first > y.first;
    }
  };
}

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