initialization of vector takes a fixed size of inputs via a constructor or any method. This can be done in five different ways: we can initialize a vector using an existing vector, array while creating an object, and most importantly, using...
vector<int> ivec {10, 11, 12}用到了c++11的新特性，初始化列表，initialize_list 而vistual studio 2012并不支持c++11这一特性。代码 vector<int> ivec(10,-1);正确，是因为 vector 存在这个版本的构造函数 explicit vector (size_type n, const value_type& val = value_type(), const...
源码跟踪 截止到现在,上述方案都没能解答本次问题的疑问,只能祭出屠龙刀,看源码了。 未初始化版调用信息如下: -> std::vector<AdItem, std::allocator<AdItem> >::vector --> std::vector<AdItem, std::allocator<AdItem> >::_M_default_initialize ---> std::__uninitialized_default_n_a<AdItem*,...
// 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...
V.resize (2*v.size) orV.resize (2*v.size, 99) doubles the capacity of V (and initializes the value of the new element to 99)3., v.empty () to determine whether the vector is empty4. vn returns the element n in the V5. v.insert ( 9、pointer, number, content) inserts the ...
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...
174explicitvector(constallocator_type &__a): _Base(__a) {}209vector(initializer_list<value_type> __l,210constallocator_type &__a =allocator_type())211: _Base(__a) {212_M_range_initialize(__l.begin(), __l.end(),random_access_iterator_tag());213}214template<typename_InputIterator...
[]) operator to initialize an array or access the elements of an array. You can store a wide variety of data types in an array element, including numbers, strings, objects, and even other arrays. You can create a multidimensional array by creating an indexed array and assigning to each ...
voidfill_initialize(size_type n,constT&value) { start=allocate_and_fill(n, value); finish= start +n; end_of_storage=finish; } 这个函数不难理解,它要做的工作主要是初始化迭代器。它接受两个参数n和value,n指明了要申请的堆空间大小,value指明了要初始化这些堆空间的内容,并把它们传给另外一个函数...
这里每个vector<A>都默认初始化为空向量，不符合要求……因为A可以默认初始化，所以构造100元素的二维向量后直接对每个元素（一维向量）resize就行：B::B(100){ for(vector< vector< A > >::iterator i = iB.begin(); i != iB.end(); ++i)i->resize(100);} 参考资料：原创 + ISO/...