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本篇学习deque的插入操作insert, emplace, 和size, max_size
insert:插入元素
emplace c++11 原位构造元素
size:返回容纳的元素个数
max_size:返回可容纳的最大元素个数
代码实现:
#include#include #include using namespace std;class Person2{public: Person2(string name): m_strName(name) { } string m_strName;};void insertElement(){ deque deque1; string strName = "《从军行(王昌龄)》青海长云暗雪山,孤城遥望玉门关。黄沙百战穿金甲,不破楼兰终不还!"; Person2 person(strName); //int = [-2147483648, 2147483647] const int count = 214748;//2147483648 double startTime1 = clock();//1计算开始 for(int i = 0; i < count; i++)//214748 { deque1.insert(deque1.begin(), strName); } double endTime1 = clock();//1时间结束 cout << "deque1.size=" << deque1.size() << " deque1.max_size=" << deque1.max_size() << endl; deque1.clear(); cout << "for 1 run time is: " << (double)(endTime1 - startTime1) / CLOCKS_PER_SEC << "s" << endl; cout << endl; deque deque2; double startTime2 = clock();//2计算开始 for(int i = 0; i < count; i++)//214748 { deque2.emplace(deque2.begin(), strName); } double endTime2 = clock();//2时间结束 cout << "deque2.size=" << deque2.size() << " deque2.max_size=" << deque2.max_size() << endl; deque2.clear(); cout << "for 2 run time is: " << (double)(endTime2 - startTime2) / CLOCKS_PER_SEC << "s" << endl; cout << endl; deque deque3; for(int i = 0; i < 3; i++)//214748 { deque3.insert(deque3.begin(), i); } cout << "deque3.size=" << deque3.size() << " deque3.max_size=" << deque3.max_size() << endl; for(auto &val: deque3) { cout << val << "\t"; } cout << endl; deque3.insert(++deque3.begin(), 50);//在第2个位置插入50 for(auto &val: deque3) { cout << val << "\t"; } cout << endl; deque3.insert(++deque3.begin(), 3, 76);//在第2个位置插入3个70 for(auto &val: deque3) { cout << val << "\t"; } cout << endl; deque deque4; for(int i = 0; i < 10; i++) { deque4.push_back(i); } //把deque4第二个位置到倒数第二个位置的值插入到deque3的第3个位置上 deque3.insert(deque3.begin() + 2, deque4.begin() + 1, deque4.end() - 1); for(auto &val: deque3) { cout << val << "\t"; } cout << endl; deque3.clear(); cout << endl;}int main(){ insertElement(); cout << endl; cout << "Hello World!" << endl; return 0;}
运行结果:
从以上可以看出emplace比insert的效率要好些,因为emplace是直接构造元素,不需要调用拷贝。
insert操作操作有以下3种方式
insert(pos,elem);//在pos位置插入一个elem元素的拷贝,返回新数据的位置。
insert(pos,n,elem);//在pos位置插入n个elem数据,无返回值。
insert(pos,beg,end);//在pos位置插入[beg,end)区间的数据,无返回值。
参考:
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