Stl_ algorithm _ Lookup algorithm (Lower_bound, Upper_bound, Equal_range)

C + + Primer learning.

。。

Simple recording of My Learning process (code-based)

Applicable for all containers (O (log (n))) ordered interval lookup algorithm

Lower_bound ()//Find the first conforming element, return position iterator

Upper_bound ()//Find the last conforming element. Return position iterator

Equal_range ()//Find a pair of iterators pair (<>,<>)

An associative container has an equivalent member function. Better performance

#include <iostream> #include <cstdio> #include <cstring> #include <vector> #include < Algorithm>using namespace std;/****************************************************************************** Std::lower_bound all sort containers for algorithm-------------------------------------- ------------------------------------------------Template <class ForwardIterator, class t> ForwardIterator Lower_bound (ForwardIterator First, ForwardIterator last, const t& value); template &L T;class ForwardIterator, Class T, class compare> ForwardIterator lower_bound (forwarditerator first, ForwardIterator Last, const t& value, Compare comp);//eg:template <class ForwardIterator, class T&G  T  ForwardIterator Lower_bound (forwarditerator first, ForwardIterator last, const t& value) {ForwardIterator it; Iterator_traits<forwarditerator>::d ifference_type Count, step;  Count = distance (first,last);    while (count>0) {it = first; step=count/2; advance (it,step);  if (*it<value)//Or:if (Comp (*it,value)), for the comp version {first=++it; count-=step+1;  } else Count=step; } return first;} *************************************************************************************//************************                           Std::upper_bound All sort containers apply Algorithm--------------------------------------------------------------------------------------template <                                Class ForwardIterator, Class t> ForwardIterator upper_bound (forwarditerator first, ForwardIterator last, const t& value); template <class ForwardIterator, class T, Class compare> ForwardIterator u Pper_bound (ForwardIterator First, ForwardIterator last, const t& value, Compare comp );//eg:template <Class ForwardIterator, Class t> ForwardIterator upper_bound (forwarditerator first, ForwardIterator last, const T&AMP ;  Value) {ForwardIterator it;  Iterator_traits<forwarditerator&gt::d ifference_type count, step;  Count = distance (first,last);    while (count>0) {it = first; step=count/2; advance (it,step); if (! (  Value<*it)//Or:if (!comp (Value,*it)), for the comp version {first=++it; count-=step+1;  } else Count=step; } return first;} *************************************************************************************//************************                           Std::equal_range All sort containers apply Algorithm--------------------------------------------------------------------------------------template < Class ForwardIterator, Class t> pair<forwarditerator,forwarditerator> Equal_range (forwarditerator first, Fo Rwarditerator last, const t& Value); template <class ForwardIterator, class T, class compare> pair<forwarditerator,forwarditerator> Equal_r Ange (ForwardIterator first, ForwardIterator last, const t& value, Compare comp);//eg:template < Class ForwardIterator, Class t> pair<forwarditerator,forwarditerator> Equal_range (forwarditerator first, Fo  Rwarditerator last, const t& value) {ForwardIterator it = Lower_bound (First,last,value); Return Make_pair (it, Upper_bound (It,last,value));} /bool mygreater (int i,int j) {return (I&GT;J);}    int main () {int myints[] = {10,20,30,30,20,10,10,20};           Vector<int> V (myints,myints+8);    Ten to ten Vector<int>::iterator low,up;                Sort (V.begin (), V.end ());    Ten-ten-cout<< "ten-ten-30\n"; Low=lower_bound (V.begin (), V.end (), 20);  //          ^  up= Upper_bound (V.begin (), V.end (), 20);    ^ cout << "Lower_bound at position" << Int (Low-v.begin ()) + 1 << Endl;    cout << "upper_bound at position" << Int (Up-v.begin ()) + 1 << Endl;    cout << Endl; /**-------------------------------------------------------------------------------**/pair<vector<int>    ::iterator,vector<int>::iterator> bounds;                              Using default comparison://sort (V.begin (), V.end ());            Ten-Bounds=equal_range (V.begin (), V.end (), 20);    ^ ^ cout<< "Ten-ten-30\n";    cout << "bounds at positions" << Int (Bounds.first-v.begin ());    cout << "and" << Int (Bounds.second-v.begin ()) << Endl;                   Using "Mygreater" as Comp:sort (V.begin (), V.end (), mygreater); Ten Bounds=equal_range (v.bEgin (), V.end (), mygreater);    ^ ^ cout<<endl<< "-Ten <<endl;    cout << "bounds at positions" << Int (Bounds.first-v.begin ());    cout << "and" << Int (Bounds.second-v.begin ()) << Endl; return 0;} /******output:10 Ten-Lower_bound at position 4 Upper_bound at position 7 10 10 10 20 2 0 bounds at positions 3 and 6, bounds at positions 2 and 5*/

Stl_ algorithm _ Lookup algorithm (Lower_bound, Upper_bound, Equal_range)