Difference between revisions of "cpp/algorithm/minmax"
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Revision as of 18:15, 2 November 2012
Template:ddcl list begin <tr class="t-dsc-header">
<td><algorithm>
<td></td> <td></td> </tr> <tr class="t-dcl ">
<td >std::pair<const T&,const T&> minmax( const T& a, const T& b );
<td > (1) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">
<td >std::pair<const T&,const T&> minmax( const T& a, const T& b, Compare comp );
<td > (2) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">
<td >std::pair<T,T> minmax( std::initializer_list<T> ilist);
<td > (3) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">
<td >std::pair<T,T> minmax( std::initializer_list<T> ilist, Compare comp );
<td > (4) </td> <td > (since C++11) </td> </tr> Template:ddcl list end
ilist.The (1,3) versions use operator< to compare the values, whereas the (2,4) versions use the given comparison function comp.
Contents |
Parameters
| a, b | - | the values to compare |
| ilist | - | initializer list with the values to compare |
| comp | - | comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if if a is less than b.The signature of the comparison function should be equivalent to the following: bool cmp(const Type1& a, const Type2& b); While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) |
| Type requirements | ||
-T must meet the requirements of LessThanComparable. for the overloads (1) and (3)
| ||
-T must meet the requirements of CopyConstructible. for the overloads (3) and (4)
| ||
Return value
a<b or if a is equivalent to b. Returns the result of std::make_pair(b, a) if b<a.ilist as the first element and the greatest as the second. If several elements are equivalent to the smallest, the leftmost such element is returned. If several elements are equivalent to the largest, the rightmost such element is returned.Complexity
ilist.size()Possible implementation
| First version |
|---|
template<class T> std::pair<const T&,const T&> minmax(const T& a, const T& b) { return (b < a) ? std::make_pair(b, a) : std::make_pair(a, b); } |
| Second version |
template<class T, class Compare> std::pair<const T&,const T&> minmax(const T& a, const T& b, Compare comp) { return comp(b, a) ? std::make_pair(b, a) : std::make_pair(a, b); } |
| Third version |
template< class T > std::pair<T,T> minmax( std::initializer_list ilist) { auto p = std::minmax_element(ilist.begin(), ilist.end()); return std::make_pair(*p.first, *p.second); } |
| Fourth version |
template< class T, class Compare > std::pair<T,T> minmax( std::initializer_list ilist, Compare comp ) { auto p = std::minmax_element(ilist.begin(), ilist.end(), comp); return std::make_pair(*p.first, *p.second); } |
Example
#include <algorithm> #include <iostream> #include <vector> #include <cstdlib> #include <ctime> int main() { std::vector<int> v {3, 1, 4, 1, 5, 9, 2, 6}; std::srand(std::time(0)); std::pair<int,int> bounds = std::minmax(std::rand() % v.size(), std::rand() % v.size()); std::cout << "v[" << bounds.first << "," << bounds.second << "]: "; for (int i = bounds.first; i < bounds.second; ++i) { std::cout << v[i] << ' '; } std::cout << '\n'; }
Possible output:
v[2,7]: 4 1 5 9 2
