strings

Table of Contents

1. String Manipulation
   • Convert Integer to String and Append
   • Remove Outer Parentheses from a String
   • Basic String Operations
   • Iterate and Transform String Characters
   • Extract Substring and Find Substring
2. cp-questions

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String Manipulation

Convert Integer to String and Append

Question: How do you convert an integer to a string, append to it, and then convert the string back to an integer?

Code Explanation:

#include<bits/stdc++.h>usingnamespacestd;intmain() {
int nums;
cin >> nums;
string s = to_string(nums); // Convert integer to string
cout << s + '1' << "\n"; // Append '1' to the string and printint n1 = stoi(s); // Convert string back to integer
cout << n1 + 1; // Add 1 to the integer and print
}

Explanation:

• Conversion: The to_string() function converts an integer nums into a string s.
• Appending:'1' is appended to s, and the result is printed.
• String to Integer: The stoi() function converts the string back to an integer, and 1 is added to it.
• Output: This demonstrates the basic conversion between strings and integers in C++.

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Remove Outer Parentheses from a String

Question: How do you remove the outermost parentheses from each primitive string in a valid parentheses string?

Code Explanation:

#include<bits/stdc++.h>usingnamespacestd;classSolution {
public:
string removeOuterParentheses(string s) {
string res = "";
int balance = 0;
for (char c : s) {
if (c == '(') {
if (balance > 0) {
res.push_back(c); // Only add '(' if it's not an outer one
}
balance += 1;
} elseif (c == ')') {
balance -= 1;
if (balance > 0) {
res.push_back(c); // Only add ')' if it's not an outer one
}
}
}
return res;
}
};

Explanation:

• Logic: This function removes the outermost parentheses in each valid primitive string.
• Balance: The balance variable keeps track of the depth of nested parentheses.
  • If the balance is positive, it means the parentheses are not outermost, so they are added to the result.
• Efficiency: This approach ensures that only the inner parentheses are kept, while the outermost ones are discarded.

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Basic String Operations

Question: How do you perform basic string operations like size, front, back, pop, push, and transform?

Code Explanation:

#include<bits/stdc++.h>usingnamespacestd;intmain() {
string s = "hello world";
cout << s << endl; // Print the string
cout << s.size() << endl; // Get size of the string
cout << s.length() << endl; // Get length of the string
cout << s.front() << endl; // Get the first character
cout << s.back() << endl; // Get the last character
s.pop_back(); // Remove the last character
s.push_back('w'); // Add 'w' to the end
cout << s.back() << endl; // Print the new last character
s.insert(0, "AKanoob "); // Insert a string at the beginning
cout << s << endl;
transform(s.begin(), s.end(), s.begin(), ::toupper); // Convert to uppercase
cout << s << endl;
transform(s.begin(), s.end(), s.begin() + 3, ::tolower); // Convert after 3rd char to lowercase
cout << s << endl;
}

Explanation:

• String Properties:size(), length(), front(), and back() provide basic information about the string.
• Modifications:pop_back(), push_back(), and insert() modify the string.
• Transformations: The transform() function is used to convert the string to uppercase and lowercase.

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Iterate and Transform String Characters

Question: How do you iterate over a string and manipulate character ASCII values?

Code Explanation:

#include<bits/stdc++.h>usingnamespacestd;intmain() {
string s = "abcd";
for (int i : s) {
cout << i << ""; // Print ASCII values of characters
}
int num = 69;
cout << (char)num << ""; // Convert ASCII value to character
cout << s[1] - s[0]; // Print difference between ASCII values of s[1] and s[0]
}

Explanation:

• Iteration: The loop iterates through each character in the string and prints its ASCII value.
• Type Casting:(char)num converts an integer to its corresponding ASCII character.
• Character Difference:s[1] - s[0] calculates the difference between ASCII values of two characters.

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Extract Substring and Find Substring

Question: How do you extract a substring from a string and find the position of a substring?

Code Explanation:

#include<bits/stdc++.h>usingnamespacestd;intmain() {
string sne = "Hy, I am a react developer!";
string s = sne.substr(4, 4); // Extract 4 characters starting from index 4
cout << s;
size_t pos = sne.find("jsjfsdfg"); // Find a substring that doesn't exist
cout << pos << endl; // Print position (will output -1 if not found)
}

Explanation:

• Extracting Substring:substr(start, length) extracts a substring starting at a specific index for a given length.
• Finding Substring:find() searches for a substring in a string and returns its position. If not found, it returns string::npos, which is typically -1.