string guide

Include Header

#include <string>

Declaration

std::string str1;                      // Empty string
std::string str2 = "Hello";           // Initialize with literal
std::string str3("World");            // Constructor form
std::string str4(5, 'x');             // "xxxxx"

String Concatenation

std::string result = str1 + str2;     // Combine strings
str1 += " more";                      // Append to existing string

Access Characters

char ch = str1[index];                // Direct access
char ch = str1.at(index);             // Bounds-checked access

Slice / Substring

std::string sub = str1.substr(start_index);           // From index to end
std::string sub = str1.substr(start_index, length);   // Substring with length

Remove Characters

str1.pop_back();                      // Remove last character
str1.erase(index, count);            // Remove count chars from index
str1.clear();                         // Clear entire string

Check if Empty

if (str1.empty()) {
    // String is empty
}

Iterate Through Characters

for (char c : str1) {
    std::cout << c << std::endl;
}

Size and Capacity

str1.size();                          // Number of characters
str1.length();                        // Same as size()
str1.capacity();                      // Allocated memory
str1.resize(new_size);               // Resize string

Reverse String

#include <algorithm>

std::reverse(str1.begin(), str1.end());

Find Substring or Character

std::size_t pos = str1.find("sub");
if (pos != std::string::npos) {
    // Found at position `pos`
}

Replace Substring

str1.replace(pos, len, "new_sub");   // Replace len characters at pos

Compare Strings

if (str1 == str2) {
    // Strings are equal
}
if (str1 < str2) {
    // Lexicographically less
}

Convert to C-style String

const char* c_str = str1.c_str();    // Null-terminated C-string

Construct from C-string

std::string str("abc");              // From literal
std::string str(cstr, length);       // From char array with length

Split String on Delimiter

#include <vector>
#include <sstream>

std::vector<std::string> split(const std::string& s, char delimiter) {
    std::vector<std::string> tokens;
    std::stringstream ss(s);
    std::string item;
    while (std::getline(ss, item, delimiter)) {
        tokens.push_back(item);
    }
    return tokens;
}

Trim Whitespace

#include <algorithm>
#include <cctype>

std::string trim(const std::string& s) {
    auto start = std::find_if_not(s.begin(), s.end(), ::isspace);
    auto end = std::find_if_not(s.rbegin(), s.rend(), ::isspace).base();
    return (start < end) ? std::string(start, end) : "";
}