Std:: vector copy, append, nested access

stl List of articles

Preface

std::vector Copy 、 Additional 、 Nested access

One 、 Copy

1. Using the copy assignment operator （ Deep copy ）, Note that the left value will be cleared first , Then copy the right value to the left value

vector<int> rightArray{
    8,3,5,2,6,4,1};
vector<int> leftArray{
    9,1,2,3};
leftArray= rightArray;

Before copying ：

After the assignment ：
The original ：leftArray Medium 9,1,2,3 It was emptied first , Then put the rightArray{ 8,3,5,2,6,4,1 }; Copied to the leftArray in

2. Make use of copy construction （ Deep copy ）

vector<int> rightArray{
     8,3,5,2,6,4,1 };
	vector<int> leftArray(rightArray);

3. utilize swap() function （ Two exchanges vector）
leftArray and rightArray The original value will be cleared first , Then exchange values with each other
Exchange before

After exchanging

4. utilize assign() function （ Empty and copy deeply ）
rightArray Will be emptied first. , Then take it. leftArray Copied to the rightArray
Before assignment

After the assignment ：

4. Memory copy （ Deep copy ）

memmove front

memmove after ：rightArray Empty the whole thing , Including redundant {4,1 Will also be emptied ,leftArray{ 9,0,7,7,0 }; Will retain