std::string::insert() in C++

insert() is used to insert characters in string at specified position. It supports various syntaxes to facilitate same, here we will describe them.

Syntax 1: Inserts the characters of str starting from index idx.

string& string::insert (size_type idx, const string& str)
idx :is the index number
str : is the string from which characters is to be picked to insert 
Returns *this.
Errors: 
Throws out_of_range if idx > size().
Throws length_error if the resulting size exceeds the maximum number of characters.
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// CPP code for insert (size_type idx, const string& str)
   
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str1, string str2)
{
   
    // Inserts str2 in str1 starting 
    // from 6th index of str1
    str1.insert(6, str2);
    cout << "Using insert : ";
    cout << str1;
}
  
// Driver code
int main()
{
    string str1("Hello World! ");
    string str2("GeeksforGeeks ");
   
    cout << "Original String : " << str1 << endl;
    insertDemo(str1, str2);
   
    return 0;
}

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Output:



Original String : Hello World! 
Using insert : Hello GeeksforGeeks World! 

Syntax 2: Inserts at most, str_num characters of str, starting with index str_idx.

string& string::insert (size_type idx, const string& str, size_type str_idx,
                                                           size_type str_num)
idx : is the index number where insertion is to be made.
str : is the string from which characters are to be picked to insert.
str_idx : is the index number in str.
str_num : is the number of characters to be inserted from str.
Returns *this.
Errors: 
Throws out_of_range if idx > size().
Throws out_of_range if str_idx > str.size().
Throws length_error if the resulting size exceeds the maximum number of characters.
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// CPP code for insert (size_type idx, const string& str, 
// size_type str_idx, size_type str_num)
   
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str1, string str2)
{
   
    // Inserts 6 characters from index number
    // 8 of str2 at index number 6 of str1 
    str1.insert(6, str2, 8, 6);
    cout << "Using insert : ";
    cout << str1;
}
  
// Driver code
int main()
{
    string str1("Hello World! ");
    string str2("GeeksforGeeks ");
   
    cout << "Original String : " << str1 << endl;
    insertDemo(str1, str2);
   
    return 0;
}

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Output:

Original String : Hello World! 
Using insert : Hello Geeks World! 

Syntax 3: Inserts the characters of the C-string cstr so that the new characters start with index idx.

string& string::insert (size_ type idx, const char* cstr)
idx : is the index number where insertion is to be made.
*cstr : is the pointer to the C-string which is to be inserted.
Returns *this.
Errors: 
Throws out_of_range if idx > size().
Throws length_error if the resulting size exceeds the maximum number of characters.

Note: cstr may not be a null pointer (NULL).

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// CPP code for insert(size_ type idx, const char* cstr)
   
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str)
{
   
    // Inserts " are " at 5th index of str
    str.insert(5, " are ");
    cout << "Using insert : ";
    cout << str;
}
  
// Driver code
int main()
{
    string str("GeeksforGeeks ");
   
    cout << "Original String : " << str << endl;
    insertDemo(str);
   
    return 0;
}

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Output:

Original String : GeeksforGeeks 
Using insert : Geeks are forGeeks 

Syntax 4: Inserts chars_len characters of the character array chars so that the new characters start with index idx.

string& string::insert (size_type idx, const char* chars, size_type chars_len)
idx : index number where insertion is to be made.
*chars : is the pointer to the array.
chars_len : is the number of characters to be inserted from character array.
Returns : *this
Errors: 
Throws out_of_range if idx > size().
Throws length_error if the resulting size exceeds the maximum number of characters.

Note : chars must have at least chars_len characters.

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// CPP code for insert (size_type idx, const char* chars, 
// size_type chars_len)
   
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str)
{
   
    // Inserts 10 characters from" are here "
    // at 5th index of str
    str.insert(5, " are here ", 10);
    cout << "Using insert : ";
    cout << str;
}
  
// Driver code
int main()
{
    string str("GeeksforGeeks ");
   
    cout << "Original String : " << str << endl;
    insertDemo(str);
   
    return 0;
}

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Output:

Original String : GeeksforGeeks 
Using insert : Geeks are here forGeeks 

Syntax 5: Inserts num occurrences of character c at the position specified by idx.

string& string ::insert (size_type idx, size_type num, char c)
idx : is the index number where insertion is to be made.
c : is the character to be inserted.
num : is the number of repetition of character c
Returns : *this
Errors: 
Throw out_of_range if idx > size().
Throw length_error if the resulting size exceeds the maximum number of characters.
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// CPP code for :insert (size_type idx, size_type num, char c)
   
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str)
{
   
    // Inserts at 5th index,
    // 5 occurrences of '$'
    str.insert(5, 5, '$');
    cout << "Using insert : ";
    cout << str;
}
  
// Driver code
int main()
{
    string str("**********");
   
    cout << "Original String : " << str << endl;
    insertDemo(str);
   
    return 0;
}

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Output:


Original String : **********
Using insert : *****$$$$$*****

Syntax 6: Inserts num occurrences of character c at the position specified by iterator pos.

void string ::insert (iterator pos, size_type num, char c)
pos : is the position of iterator.
c : is the character which is to be inserted.
Returns : *this
Errors: 
Throws out_of_range if pos > size().
Throws length_error if the resulting size exceeds the maximum number of characters.
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// CPP code for :insert (iterator pos, size_type num, char c)
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str)
{
   
    // Inserts 5 occurrences of '$'
    // at position str.begin() + 5
    str.insert(str.begin() + 5, 5, '$');
    cout << "Using insert : ";
    cout << str;
}
  
// Driver code
int main()
{
    string str("**********");
   
    cout << "Original String : " << str << endl;
    insertDemo(str);
   
    return 0;
}

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Output:

Original String : **********
Using insert : *****$$$$$*****

Syntax 7: Inserts a copy of character c before the character to which iterator pos refers.

iterator string ::insert (iterator pos, char c )
pos : is the position of iterator.
c : is the character which is to be inserted.
Returns :  iterator pointing to the first character inserted.
Error: 
Throws length_error if the resulting size exceeds the maximum number of characters.
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// CPP code for :insert (iterator pos, char c )
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str)
{
     std::string::iterator pos;
  
    // Inserts '$' at position
    //  str.begin() + 5
    pos = str.insert(str.begin()+5,'$');
    cout << "Using insert : ";
    cout << str << endl;
    cout << "Value at Iterator returned : " << *pos;
      
}
  
// Driver code
int main()
{
    string str("**********");
   
    cout << "Original String : " << str << endl;
    insertDemo(str);
   
    return 0;
}

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Output:

Original String : **********
Using insert : *****$*****
Value at Iterator returned : $

Syntax 8: Inserts all characters of the range [ beg,end ) before the character to which iterator pos refers.

void string ::insert (iterator pos, InputIterator beg, InputIterator end )
pos : is the iterator position.
beg, end : Input iterators to the initial and final positions in a sequence.
Error: 
Throws length_error if the resulting size exceeds the maximum number of characters.
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// CPP code for insertinsert (iterator pos, InputIterator beg,
// InputIterator end )
   
#include <iostream>
#include <string>
  
using namespace std;
   
// Function to demonstrate insert
void insertDemo(string str1, string str2)
{
   
    // Inserts str2.begin() + 5 ,  str2.end() - 6
    // at position str1.begin() + 6
    str1.insert(str1.begin() + 6, str2.begin() + 5 ,  str2.end() - 6);
    cout << "Using insert : ";
    cout << str1;
}
  
// Driver code
int main()
{
    string str1("Hello  World! ");
    string str2("GeeksforGeeks ");
   
    cout << "Original String : " << str1 << endl;
    insertDemo(str1, str2);
   
    return 0;
}

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Output:

Original String : Hello World! 
Using insert : Hello forWorld! 

This article is contributed by Sakshi Tiwari. If you like GeeksforGeeks(We know you do!) and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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