在C ++中将字符串转换为int

In this article, we will look at how we can convert a string to int in C++. Often, we may need to convert numeral strings into integers. We may need certain ways to quickly do the conversion

在本文中，我们将研究如何在C ++中将字符串转换为int。通常，我们可能需要将数字字符串转换为整数。我们可能需要某些方法来快速进行转换

Let’s take a look at various ways to convert a string to int.

让我们看一下将字符串转换为int的各种方法。

方法1 –使用std :: stoi (Method 1 – Using std::stoi)

To convert a std::string object to an integer, this is the recommended option in C++. This takes in a string as input and returns an integer.

要将std::string对象转换为整数，这是C ++中的推荐选项。这将字符串作为输入并返回整数。

Here is a simple example:

这是一个简单的示例：


#include <iostream>
#include <string>using namespace std;int main() {string inp = "102";cout << "Input String: " << inp << endl;// Use std::stoi() to convert string to integerint res = stoi(inp);cout << "Integer: " << res << endl;return 0;
}

Output

输出量


Input String: 102
Integer: 102

This will work for negative value strings also.

这也适用于负值字符串。

However, this will throw a std::invalid_argument exception if the string is not of the proper format.

但是，如果字符串格式不正确，则会抛出std::invalid_argument异常。

Because of this, we must use Exception Handling in our code, if the string is not validated.

因此，如果未验证字符串，则必须在代码中使用异常处理。


#include <iostream>
#include <string>using namespace std;int main() {string inp = "Hello";cout << "Input String: " << inp << endl;// Use std::stoi() to convert string to integertry {// Wrap up code in try-catch block if string is not validatedint res = stoi(inp);cout << "Integer: " << res << endl;}catch(std::invalid_argument e) {cout << "Caught Invalid Argument Exception\n";}return 0;
}

Output

输出量


Input String: Hello
Caught Invalid Argument Exception

Hopefully that gives you a good idea of how you can convert a String into a Integer in C++.

希望这对如何在C ++中将String转换为Integer有所帮助。

We’ll also present one more way, using the C-style atoi() function.

我们还将使用C风格的atoi()函数展示另一种方法。

方法2 –使用atoi（） (Method 2 – Using atoi())

We can convert a C string (char*) into an integer, using atoi(char* str).

我们可以使用atoi(char* str)将C字符串（ char* ）转换为整数。

We can apply this logic to our std::string object, by first converting into a C string.

通过首先转换为C字符串，可以将此逻辑应用于std::string对象。


#include <iostream>
#include <string>using namespace std;int main() {string inp = "120";cout << "Input String: " << inp << endl;// Convert std::string to C-stringconst char* c_inp = inp.c_str();// Use atoi() to convert C-string to integerint res = atoi(c_inp);cout << "Integer: " << res << endl;return 0;
}

Output

输出量


Input String: 120
Integer: 120

As you can see, this gives us the same result as before!

如您所见，这为我们提供了与以前相同的结果！

结论 (Conclusion)

In this article, we learned how we could convert a string to int in C++.

在本文中，我们学习了如何在C ++中将字符串转换为int。

For similar content, do go through our tutorial section on C++ programming.

对于类似的内容，请阅读我们有关C ++编程的教程部分。

参考资料 (References)

StackOverflow Question on converting string to int in C++在C ++中将字符串转换为int的StackOverflow问题

翻译自: https://www.journaldev.com/41723/convert-string-int-c-plus-plus