lower_bound和upper_bound的用法？

[wang37921]

在msdn上面查找lower_bound：
Returns an iterator to the first element in a hash_map with a key value that is equal to or greater than that of a specified key.
使用它的例子

// hash_map_lower_bound.cpp
// compile with: /EHsc
#define _DEFINE_DEPRECATED_HASH_CLASSES 0
#include <hash_map>
#include <iostream>

int main( )
{
   using namespace std;
   using namespace stdext;
   hash_map <int, int> hm1;
   hash_map <int, int> :: const_iterator hm1_AcIter, hm1_RcIter;
   typedef pair <int, int> Int_Pair;

   hm1.insert ( Int_Pair ( 1, 10 ) );
   //改动处
   //hm1.insert ( Int_Pair ( 2, 20 ) );
   hm1.insert ( Int_Pair ( 3, 30 ) );

   hm1_RcIter = hm1.lower_bound( 2 );
   cout << "The first element of hash_map hm1 with a key of 2 is: "
        << hm1_RcIter -> second << "." << endl;

   // If no match is found for the key, end( ) is returned
   hm1_RcIter = hm1. lower_bound ( 4 );

   if ( hm1_RcIter == hm1.end( ) )
      cout << "The hash_map hm1 doesn't have an element "
           << "with a key of 4." << endl;
   else
      cout << "The element of hash_map hm1 with a key of 4 is: "
           << hm1_RcIter -> second << "." << endl;

   // An element at a specific location in the hash_map can be 
   // found using a dereferenced iterator addressing the location
   hm1_AcIter = hm1.end( );
   hm1_AcIter--;
   hm1_RcIter = hm1. lower_bound ( hm1_AcIter -> first );
   cout << "The element of hm1 with a key matching "
        << "that of the last element is: "
        << hm1_RcIter -> second << "." << endl;
}

hm1.insert ( Int_Pair ( 2, 20 ) );
这一行注释掉了～这个lower_bound不是应该返回3吗？怎么是个end啊。。。

[taodm]

这个，楼主还是买本《stl源码剖析》吧

[chenyu2202863]

就是二分查找

[cattycat]

注意你用的是hash_map的lower_bound成员函数，不是stl中lower_bound算法库函数。所以你查的msdn解释的不是这个，你去看hash_map的成员函数lower_bound是怎么说明的。

[wang37921]

map的是不小于～
和hashmap不一样～
但是msdn上的解释的确是hashmap的。。。。