C++ In a Nutshell

Name

lexicographical_compare function template — Compares ranges for less-than

Synopsis

template<typename InIter1, typename InIter2>
  bool lexicographical_compare(InIter1 first1, InIter1 last1, InIter2 first2,
                               InIter2 last2);
template<typename InIter1, typename InIter2, typename Compare> 
  bool lexicographical_compare(InIter1 first1, InIter1 last1, InIter2 first2,
                               InIter2 last2, Compare comp);

The lexicographical_compare function template returns true if the sequence [first1, last1) is less than the sequence [first2, last2). If the sequences have the same length and contents, the return value is false. If the second sequence is a prefix of the first, true is returned. (The use of “lexicographical” emphasizes that the ranges are compared element-wise, like letters in words.)

The first form uses the < operator to compare elements. The second form calls comp(*iter1, *iter2).

Technical Notes

Let length1 = last1 - first1, length2 = last2 - first2, and minlength = min(length1, length2).

The lexicographical_compare function template returns true if either of the following conditions is true:

• There is an n in [0, minlength) such that *(first1 + m) == *(first2 + m) for all m in [0, n - 1), and *(first1 + n) < *(first2 + n).

• *(first1 + n) == *(first2 + n) for all n in [0, length2) and length2 < length1.

Complexity is linear: at most, minlength comparisons are performed.

Example

#include <algorithm> #include <iostream> #include <ostream> int main( ) { using namespace std; int a[] = { 1, 10, 3, 42 }; int ...