C++

Though strings can be represented as an array of characters, most languages have a separate type for strings.

Include statement: #include <string>

Let’s see the string type in C++ and some of its methods that we will be using frequently.

The entire documentation can be found here.

string s; // new empty string

s.size(); // get size()
s[i]; // access character 

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Time complexity

The string data type is an array of characters and hence the operations are very similar to that on a vector; memory, time and name-wise. Points to note are

• Inserting at the end - $O(1)$
• Inserting in between - $O(N)$
• Deleting last character - $O(1)$
• Deleting other characters - $O(N)$

A quick recap, inserting or deleting middle characters requires the shifting of other characters.

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Append

string has multiple methods to append to an existing string.

• $append(s)$ - append another string
• += $operator$ - append another string
• $push\_back(c)$ - append character

string s1;
string s2 = "str";

s1.append(s2); // s1 = "str"
s1.push_back('i'); // s1 = "stri"
s1+="ng"; // s1 = "string"

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Delete

• $erase(it)$ - Iterator to the character to remove
• $erase(pos, len)$ - erase len number of characters starting at position pos

string s = "example string";

s.erase(s.begin() + 7); // s = "examplestring"
s.erase(4, 6); // s = "examing"

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Substring

The substring substr(start_pos, len) returns substring for passed start position and length (length is optional, if skipped, return the string till the end).

Here is a code snippet where the functions return lo W. Fix it to return Hell to pass the test.