map::lower_bound

返回迭代器到映射的第一个元素与等于或大于一指定键的键值。

iterator lower_bound(
   const Key& _Key
);
const_iterator lower_bound(
   const Key& _Key
) const;

参数

• _Key
  参数键值用一个元素的排序关键字进行比较从要搜索的映射。

返回值

解决一个元素位置在映射中使用键等于或大于参数键，或者解决成功最后一个元素的位置映射中 iterator 或 const_iterator，如果与未作为项中。

如果 lower_bound 的返回值赋给 const_iterator，不能修改映射对象。如果 lower_bound 的返回值赋给 iterator，可以修改映射对象。

示例

// map_lower_bound.cpp
// compile with: /EHsc
#include <map>
#include <iostream>

int main( )
{
   using namespace std;   
   map <int, int> m1;
   map <int, int> :: const_iterator m1_AcIter, m1_RcIter;
   typedef pair <int, int> Int_Pair;

   m1.insert ( Int_Pair ( 1, 10 ) );
   m1.insert ( Int_Pair ( 2, 20 ) );
   m1.insert ( Int_Pair ( 3, 30 ) );

   m1_RcIter = m1.lower_bound( 2 );
   cout << "The first element of map m1 with a key of 2 is: "
        << m1_RcIter -> second << "." << endl;

   // If no match is found for this key, end( ) is returned
   m1_RcIter = m1. lower_bound ( 4 );

   if ( m1_RcIter == m1.end( ) )
      cout << "The map m1 doesn't have an element "
           << "with a key of 4." << endl;
   else
      cout << "The element of map m1 with a key of 4 is: "
           << m1_RcIter -> second << "." << endl;

   // The element at a specific ___location in the map can be found 
   // using a dereferenced iterator addressing the ___location
   m1_AcIter = m1.end( );
   m1_AcIter--;
   m1_RcIter = m1. lower_bound ( m1_AcIter -> first );
   cout << "The element of m1 with a key matching "
        << "that of the last element is: "
        << m1_RcIter -> second << "." << endl;
}

要求

标头: <map>

命名空间: std

请参见

参考

map Class

标准模板库