vector insert()

1. 语法：

vector_name.insert (position, val)

- position：插入的位置；

- val：插入的值；

Return value：返回一个迭代器Iterator，指向新插入的元素。

// program below illustrates the 
// vector::insert() function 

#include <bits/stdc++.h> 
using namespace std; 

int main() 
{ 
    // initialising the vector 
    vector<int> vec = { 10, 20, 30, 40 }; 

    // inserts 3 at front 
    auto it = vec.insert(vec.begin(), 3); 
    
    // inserts 2 at front 
    vec.insert(it, 2); 

    cout << "The vector elements are: "; 
    for (auto it = vec.begin(); it != vec.end(); ++it) 
        cout << *it << " "; 

    return 0; 
} 

Output:

The vector elements are: 2 3 10 20 30 40

2. 语法：

vector_name.insert(position, size, val)

- position：插入的位置；

- val：插入的值；

- size：插入值的个数；

Return value：返回一个迭代器Iterator，指向新插入的元素。

// program below illustrates the 
// vector::insert() function 

#include <bits/stdc++.h> 
using namespace std; 

int main() 
{ 
    // initialising the vector 
    vector<int> vec = { 10, 20, 30, 40 }; 

    // inserts 3 one time at front 
    auto it = vec.insert(vec.begin(), 1, 3); 
    
    // inserts 4 two times at front 
    vec.insert(it, 2, 4); 

    cout << "The vector elements are: "; 
    for (auto it = vec.begin(); it != vec.end(); ++it) 
        cout << *it << " "; 

    return 0; 
} 

Output:

The vector elements are: 4 4 3 10 20 30 40

3. 语法：

vector_name.insert(position, iterator1 , iterator2)

- position：插入的位置；

- iterator1 ：插入元素的开始位置；

- iterator2 ：插入元素的结束位置；

Return value：返回一个迭代器Iterator，指向新插入的元素。

// program below illustrates the 
// vector::insert() function 

#include <bits/stdc++.h> 
using namespace std; 

int main() 
{ 
    // initialising the vector 
    vector<int> vec1 = { 10, 20, 30, 40 }; 
    vector<int>vec2; 
    
    // inserts at the beginning of vec2 
    vec2.insert(vec2.begin(),vec1.begin(),vec1.end()); 

    
    cout << "The vector2 elements are: "; 
    for (auto it = vec2.begin(); it != vec2.end(); ++it) 
        cout << *it << " "; 

    return 0; 
} 

参考链接：https://www.geeksforgeeks.org/vector-insert-function-in-c-stl/