C++之lexicographical_compare

lexicographical_compare： C++ STL 泛型算法函数：用于按字典序比较两个序列。

函数申明：

/**

重载1

如果[first1, last1)按字典序列小于[first2, last2)，返回true，否则返回false。

template <class InputIterator1, class InputIterator2 >

bool lexicographical_compare( InputIterator1 first1, InputIterator1 last1,

　　 InputIterator2 first2, InputIterator2 last2 );

/**

重载2

功能同重载1，增加了比较函数comp，即大小关系由comp函数确定。

template < class InputIterator1, class InputIterator2,

class Compare >

bool lexicographical_compare( InputIterator1 first1, InputIterator1 last1,

　　 InputIterator2 first2, InputIterator2 last2,

　　 Compare comp );

For example:

View Code

 1 // alg_lex_comp.cpp
 2 // compile with: /EHsc
 3 #include <vector>
 4 #include <list>
 5 #include <algorithm>
 6 #include <iostream>
 7 
 8 // Return whether second element is twice the first
 9 bool twice ( int elem1, int elem2 )
10 {
11    return 2 * elem1 < elem2;
12 }
13 
14 int main( )
15 {
16    using namespace std;
17    vector <int> v1, v2;
18    list <int> L1;
19    vector <int>::iterator Iter1, Iter2;
20    list <int>::iterator L1_Iter, L1_inIter;
21 
22    int i;
23    for ( i = 0 ; i <= 5 ; i++ )
24    {
25       v1.push_back( 5 * i );
26    }
27    int ii;
28    for ( ii = 0 ; ii <= 6 ; ii++ )
29    {
30       L1.push_back( 5 * ii );
31    }
32 
33    int iii;
34    for ( iii = 0 ; iii <= 5 ; iii++ )
35    {
36       v2.push_back( 10 * iii );
37    }
38 
39    cout << "Vector v1 = ( " ;
40    for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
41       cout << *Iter1 << " ";
42    cout << ")" << endl;
43 
44    cout << "List L1 = ( " ;
45    for ( L1_Iter = L1.begin( ) ; L1_Iter!= L1.end( ) ; L1_Iter++ )
46       cout << *L1_Iter << " ";
47    cout << ")" << endl;
48 
49    cout << "Vector v2 = ( " ;
50    for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
51       cout << *Iter2 << " ";
52       cout << ")" << endl;
53 
54    // Self lexicographical_comparison of v1 under identity
55    bool result1;
56    result1 = lexicographical_compare (v1.begin( ), v1.end( ),
57                   v1.begin( ), v1.end( ) );
58    if ( result1 )
59       cout << "Vector v1 is lexicographically_less than v1." << endl;
60    else
61       cout << "Vector v1 is not lexicographically_less than v1." << endl;
62 
63    // lexicographical_comparison of v1 and L2 under identity
64    bool result2;
65    result2 = lexicographical_compare (v1.begin( ), v1.end( ),
66                   L1.begin( ), L1.end( ) );
67    if ( result2 )
68       cout << "Vector v1 is lexicographically_less than L1." << endl;
69    else
70       cout << "Vector v1 is lexicographically_less than L1." << endl;
71 
72    bool result3;
73    result3 = lexicographical_compare (v1.begin( ), v1.end( ),
74                   v2.begin( ), v2.end( ), twice );
75    if ( result3 )
76       cout << "Vector v1 is lexicographically_less than v2 "
77            << "under twice." << endl;
78    else
79       cout << "Vector v1 is not lexicographically_less than v2 "
80            << "under twice." << endl;
81 }
82 /*
83 Output:
84 
85 Vector v1 = ( 0 5 10 15 20 25 )
86 List L1 = ( 0 5 10 15 20 25 30 )
87 Vector v2 = ( 0 10 20 30 40 50 )
88 Vector v1 is not lexicographically_less than v1.
89 Vector v1 is lexicographically_less than L1.
90 Vector v1 is not lexicographically_less than v2 under twice.
91 */