矢量比较失败

Question

我正在尝试比较两个向量，据我所知，向量支持关系运算符，它的工作方式如下：比较 v1 中的第一个元素与 v2 中的第一个元素，依此类推..

为什么以下代码的结果是 (true) where the last element in v1 > v2 ?!

#include  <iostream>
#include  <vector>
using namespace std;

void main()
{

    vector <int> V1 = { 2,1,0,3 };
    vector <int> V2 = { 3,4,2,2 };

    cout << (V1 <= V2);  //print true !!


    system("pause");
}

Answer 1

operator==,!=,<,<=,>,>= 比较两个向量字典序的内容。来自 http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare :

Lexicographical comparison is a operation with the following properties:

Two ranges are compared element by element.

The first mismatching element defines which range is lexicographically less or greater than the other.

这就是字符串“abcdx”小于“abced”和[的原因2,1,0,3] 小于 [3,4,2,2].

Answer 2

std::vector是一个数据容器，除了包含多个元素外，与向量的数学概念无关。

std::vector 的 doc 说明了比较的工作原理：

The equality comparison (operator==) is performed by first comparing sizes, and if they match, the elements are compared sequentially using operator==, stopping at the first mismatch (as if using algorithm equal).

The less-than comparison (operator<) behaves as if using algorithm lexicographical_compare, which compares the elements sequentially using operator< in a reciprocal manner (i.e., checking both a

矢量比较失败

Fail of Vectors Comparison

c++

std

stdvector