Vector中两个元素值的交换

 swap是可以交换vector的变量
代码如下
int   main(int   argc,   char*   argv[])
{
std::vector <string>   sentence;
sentence.push_back( "hello ");
sentence.push_back( "how ");
sentence.push_back( "are ");
sentence.push_back( "you ");
sentence.push_back( "csdn ");
swap(   sentence[0]   ,sentence[4]   );
return   0;
}