Originally, I was adding 3 elements to the vector using push_back() in a loop. To improve the performance, I decided to initialize the vector with a fixed size of 3 upfront, like this: vector t(3, 0). Surprisin
1voidfill_initialize(size_type n,constT&value) {2start = allocate_and_fill(n, value);//配置空间并设置空间的首端3finish = start + n;//设置使用空间的尾端4end_of_storage = finish;//使用总空间的尾端5} 我们发现这个函数只是负责初始化容器3个管理空间的迭代器,而真正配置空间的还另有其人:al...
val);}//n个元素为val值//填充并且初始化voidfill_initialize(size_typen,constvalue_type&val){start=allocate_and_fill(n,val);//起始地址finish=begin()+n;//元素结束地址end_of_storage=finish;//总容量结束地址}iteratorallocate_and_fill(size_typen,constvalue_type&val){iteratorres=data_allocator::...
1,Vector的效率差不多是Array的3倍,这里就不在证明了,Array的初始化相当的简单: var $arr = []; var $arr = [1,2,3]; 现在来谈谈Vector的初始化: var $strV : Vector.<String> = new Vector.<String>(); var $strV : Vector.<String> = new <String>["1","2","3"];//*注意此处没有 ...
// initialize vectors x,y,z and w. for(int i=0; i<N_VECTORS; ++i) { foo[i].x = float(rand() % 10); foo[i].y = float(rand() % 10); foo[i].z = float(rand() % 10); foo[i].w = 1; } 注意上面的元素索引使用容器的'[]'操作符. 这不是最快的方式, 因为操作符函数...
289 vector(size_type __n, const value_type& __value, 290 const allocator_type& __a = allocator_type()) 291 : _Base(__n, __a) 292 { _M_fill_initialize(__n, __value); } 整个初始化分为了三部分: 第一部分 : 构造函数链 初始化基类_Base。这里有一个构造函数链,我会详细说明...
Reference operator[]( size_type n) { return *(begin()+n);} //借用迭代器完成随机访问 Vector(): start(0),finish(0),end_of_storage(0) {} Vector( size_type n, const T& value) { fill_initialize(n,value);} //分配T型的空间 ...
{ _M_fill_initialize(__n, __value); } //拷贝构造函数 vector(const vector& __x) : _Base(__x.size(), _Alloc_traits::_S_select_on_copy(__x._M_get_Tp_allocator())) { this->_M_impl._M_finish = std::__uninitialized_copy_a(__x.begin(), __x.end(), this->_M_impl....
= v1.end(); Iter++) cout << " " << *Iter; cout << endl; // initialize a vector of vectors by moving v1 vector<vector<int>> vv1; vv1.insert(vv1.begin(), move(v1)); if (vv1.size() != 0 && vv1[0].size() != 0) { cout << "vv1[0] ="; for (Iter = vv...
explicit vector(size_type count);initializes the controlled sequence with count elements each with value value_type(). You use it to fill the container with elements all having the default value.The constructor:vector(size_type count, value_type val);...