Отправлено: 23.06.14 18:06. Заголовок: replace first value and last value in a vector

how can i replace first element and last element in a vector i try to insert but its append value to it . my vector values -> {1,5,2,4,5,47} i need to replace value first value 1 , and last value 47, with other value how can i do that

#include <iostream>
#include <vector>

using namespace std;

const int x = 6;
int main() {


int a[x]={1,5,2,4,5,47};

vector<int> v(a,a+x);

int c = v.size();

v.insert(v.begin(),5);

for(int f = 0; f<v.size();f++){

cout<<v[f]<<endl;

}




return 0;
}

 Отправлено: 23.06.14 18:41. Заголовок: You can use member f..

You can use member functions front() and back() or the subscript operator. For example

 
 #include <iostream> 
 #include <vector> 
  
 int main() 
 { 
 	std::vector<int> v = { 1, 5, 2, 4, 5, 47 };  
 		 
 	for ( int x : v ) std::cout << x << ' '; 
 	std::cout << std::endl; 
 		 
 	v.front() = 5; v.back() = 5; 
 //	v[0] = 5; v[v.size() - 1] = 5; 
 		 
 	for ( int x : v ) std::cout << x << ' '; 
 	std::cout << std::endl; 
  
 	return 0; 
 } 
 

The output is

 
 1 5 2 4 5 47  
 5 5 2 4 5 5  
 

If you mean to exchange the first and the last elements of a vector then you can write simply

 
 std::swap( v.front(), v.back() );