admin管理员组

文章数量:1611915

vector的capacity()调用返回vector中最大能够存储的元素个数，也即在下一次需要扩充容量之前能容纳的元素个数。reserve会使容器在必要的时候增长，以便容纳制指定数目的元素。 
#include <iostream>
#include <vector>
using namespace std;
int main(int argc, char *argv[])
{
 vector<int> v, u;
 v.reserve(5);
 cout << v.capacity() <<endl;   //5 
 v.resize(10);
 cout << v.capacity() <<endl;   //10
 cout << "Initial capaciry of u: " << u.capacity() <<endl;
 for(int i = 0; i < 40; ++i) 
 {
    u.push_back(i);
    cout << "Now capacity is :" << u.capacity() <<"    i:   "<<i<<endl;
 }
 
 return 0;
}

结果：

5
10
Initial capaciry of u: 0
Now capacity is :1    i:   0
Now capacity is :2    i:   1
Now capacity is :4    i:   2
Now capacity is :4    i:   3
Now capacity is :8    i:   4
Now capacity is :8    i:   5
Now capacity is :8    i:   6
Now capacity is :8    i:   7
Now capacity is :16    i:   8
Now capacity is :16    i:   9
Now capacity is :16    i:   10
Now capacity is :16    i:   11
Now capacity is :16    i:   12
Now capacity is :16    i:   13
Now capacity is :16    i:   14
Now capacity is :16    i:   15
Now capacity is :32    i:   16
Now capacity is :32    i:   17
Now capacity is :32    i:   18
Now capacity is :32    i:   19
Now capacity is :32    i:   20
Now capacity is :32    i:   21
Now capacity is :32    i:   22
Now capacity is :32    i:   23
Now capacity is :32    i:   24
Now capacity is :32    i:   25
Now capacity is :32    i:   26
Now capacity is :32    i:   27
Now capacity is :32    i:   28
Now capacity is :32    i:   29
Now capacity is :32    i:   30
Now capacity is :32    i:   31
Now capacity is :64    i:   32
Now capacity is :64    i:   33
Now capacity is :64    i:   34
Now capacity is :64    i:   35
Now capacity is :64    i:   36
Now capacity is :64    i:   37
Now capacity is :64    i:   38
Now capacity is :64    i:   39


--------------------------------
Process exited after 0.05695 seconds with return value 0
请按任意键继续. . .



本文标签： 增长方式VectorCapacitydev

版权声明：本文标题：vector的capacity新增长方式（dev c++实测） 内容由热心网友自发贡献，该文观点仅代表作者本人， 转载请联系作者并注明出处：https://www.elefans.com/dianzi/1728622517a1166535.html， 本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容，一经查实，本站将立刻删除。