Common string processing problems and solutions in C++

Common string processing problems and solutions in C

Introduction
String processing is one of the problems often encountered in C programming. Whether it is input from the user, reading data from a file, or processing and converting data, string processing always occupies an important position. This article will introduce common string processing problems in C, give corresponding solutions, and provide specific code examples.

Question 1: String length
Sometimes, we need to get the length of a string. This is a common string processing problem. C provides two ways to get the length of a string: using the C string library functions and using the string class of the C standard library.

Solution 1: Use the C string library function
The C string library function provides a function named strlen for obtaining the length of a string. The following is a sample code:

#include <iostream>
#include <cstring>

int main() {
   const char* str = "Hello, world!";
   int len = strlen(str);
   std::cout << "The length of string is " << len << std::endl;
   return 0;
}

Solution 2: Use the string class of the C standard library
The string class of the C standard library provides a member function named size for obtaining strings length. The following is a sample code:

#include <iostream>
#include <string>

int main() {
   std::string str = "Hello, world!";
   int len = str.size();
   std::cout << "The length of string is " << len << std::endl;
   return 0;
}

Question 2: String comparison
In string processing, string comparison operations are often required. Comparing strings can be used to determine whether two strings are equal, and to determine the position of one string within another string.

Solution: Use the C string library functions or the string class of the C standard library

1. Use the C string library functions
   The C string library functions provide a name It is a function of strcmp, used to compare two strings. The following is a sample code:

#include <iostream>
#include <cstring>

int main() {
   const char* str1 = "Hello";
   const char* str2 = "World";
   int result = strcmp(str1, str2);
   if (result == 0) {
      std::cout << "The two strings are equal." << std::endl;
   } else if (result < 0) {
      std::cout << "The first string is less than the second string." << std::endl;
   } else {
      std::cout << "The first string is greater than the second string." << std::endl;
   }
   return 0;
}

2. Using the string class of the C standard library
   The string class of the C standard library provides an overloaded "==" operator, String comparisons can be performed directly. The following is a sample code:

#include <iostream>
#include <string>

int main() {
   std::string str1 = "Hello";
   std::string str2 = "World";
   if (str1 == str2) {
      std::cout << "The two strings are equal." << std::endl;
   } else {
      std::cout << "The two strings are not equal." << std::endl;
   }
   return 0;
}

Question 3: Convert string to number
Sometimes, we need to convert string to integer or floating point number. This is a common string processing problem, and C provides corresponding functions to convert strings to numbers.

Solution: Use the string class and related functions of the C standard library
The string class of the C standard library provides a function named stoi for converting strings to integers. The following is a sample code:

#include <iostream>
#include <string>

int main() {
   std::string str = "12345";
   int num = std::stoi(str);
   std::cout << "The number is " << num << std::endl;
   return 0;
}

If you need to convert a string to a floating point number, you can use the stof function. The following is a sample code:

#include <iostream>
#include <string>

int main() {
   std::string str = "3.14";
   float num = std::stof(str);
   std::cout << "The number is " << num << std::endl;
   return 0;
}

Conclusion
String processing is one of the common problems in C programs. This article introduces common string processing problems in C and gives corresponding solutions. scheme, and provides specific code examples. I hope these examples can help readers better understand and master string processing techniques in C. Of course, these are only some common problems and solutions. In actual applications, more practical situations will be encountered, which need to be handled accordingly according to specific needs.

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