【函数】fill和fill_n填充之区别

fill对区间填充

原型:

template < class ForwardIterator, class T >

void fill ( ForwardIterator first, ForwardIterator last, const T& value )

{

  while (first != last)  *first++ = value;

}

填充区间[first,last)

示例：

#include <iostream>

#include <algorithm>

#include <vector>

using namespace std;



int main () {

  vector<int> myvector (8);                       // myvector: 0 0 0 0 0 0 0 0



  fill (myvector.begin(),myvector.begin()+4,5);   // myvector: 5 5 5 5 0 0 0 0

  fill (myvector.begin()+3,myvector.end()-2,8);   // myvector: 5 5 5 8 8 8 0 0



  cout << "myvector contains:";

  for (vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)

    cout << " " << *it;



  cout << endl;

 

  return 0;

}

fill_n可指定填充的个数

原型:

template < class OutputIterator, class Size, class T >

  void fill_n ( OutputIterator first, Size n, const T& value )

{

  for (; n>0; --n)  *first++ = value;

}

填充区间[first，first+n)

n为要填充的元素个数

示例：

#include <iostream>

#include <algorithm>

#include <vector>

using namespace std;



int main () {

  vector<int> myvector (8,10);        // myvector: 10 10 10 10 10 10 10 10



  fill_n (myvector.begin(),4,20);     // myvector: 20 20 20 20 10 10 10 10

  fill_n (myvector.begin()+3,3,33);   // myvector: 20 20 20 33 33 33 10 10



  cout << "myvector contains:";

  for (vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)

    cout << " " << *it;



  cout << endl;

 

  return 0;

}