对比array是静态空间一旦配置了就不能改变大小。 vector的动态增加大小的时候,并不是在原有的空间上持续新的空间(无法保证原空间的后面还有可供配置的空间),而是以原大小的两倍另外配置一块较大的空间,然后将原内容拷贝过来,并释放原空间。在VS下是1.5倍扩容,在GCC下是2倍扩容。 在原来空间不够存储新值时,每次...
//vector<int>::iterator it; //C++11之前用的,11之后可以用auto for(autoit=num.begin(); it!=num.end(); ++it) { cout << *it <<" "; } cout << endl; num.insert(num.begin()+2,3,10);//在num[2]之前加3个10 cout <<"Inserted array:\n"; for(autoit=num.begin(); it!=num....
cpp复制编辑class JsonValue {public: enum class Type { Null, Number, String, Bool, Array, Object };private: Type type; std::variant<std::nullptr_t, double, std::string, bool, std::vector<JsonValue>, std::map<std::string, JsonValue>> value;public: JsonValue(); // Null JsonValue(d...
are stored contiguously, which means that elements can be accessed not only through iterators, but also using offsets to regular pointers to elements. This means that a pointer to an element of a vector may be passed to any function that expects a pointer to an element of an array. ...
How to delete element from Vector: There is tricky thing for deleting in vector loop. The erase method returns the next element after the one you just erased. So you can use that to continue in your loop. vector c; iterator i = c.begin(); ...
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vector resizable contiguous array (class template) deque double-ended queue (class template) make_array (library fundamentals TS v2) creates astd::arrayobject whose size and optionally element type are deduced from the arguments (function template)...
typedef array<int, 3> ARR; typedef vector<int> VI; typedef vector<double> VDB; typedef vector<string> VS; typedef vector<PII> VPII; typedef vector<ARR> VARR; typedef vector<VI> VVI; typedef vector<VDB> VVDB; typedef vector<VPII> VVPII; typedef unordered_map<int,int> ...
你向vector中push了2个元素,此时vector的实际内存是为4个的。这是你再向vector中push一个元素,因为vector还有2个未用的空间,所以不需要申请内存。这样就可以在原来那块已经分配好的内存中调用元素的构造函数就可以了。而这里就恰恰用到了placement new了。
array 数组 随机读改 O(1) 无序 可重复 支持随机访问 vector 数组 随机读改、尾部插入、尾部删除 O(1)头部插入、头部删除 O(n) 无序 可重复 支持随机访问 deque 双端队列 头尾插入、头尾删除 O(1) 无序 可重复 一个中央控制器 + 多个缓冲区,支持首尾快速增删,支持随机访问 forward_list 单向链表 插入、...