在C++中从字符串中提取后4个字符_在C中从字符串中提取后4个字符_postgresql从文本值中移除后4个字符 - 腾讯云开发者社区

在C++中从字符串中提取后4个字符

在C++中，从字符串中提取后4个字符可以通过多种方式实现。以下是几种常见的方法：

方法一：使用`substr`方法

#include <iostream>
#include <string>

int main() {
    std::string str = "Hello, World!";
    int len = str.length();

    if (len >= 4) {
        std::string lastFour = str.substr(len - 4);
        std::cout << "Last 4 characters: " << lastFour << std::endl;
    } else {
        std::cout << "String is too short to extract 4 characters." << std::endl;
    }

    return 0;
}

方法二：使用循环手动提取

#include <iostream>
#include <string>

int main() {
    std::string str = "Hello, World!";
    int len = str.length();
    std::string lastFour = "";

    if (len >= 4) {
        for (int i = len - 4; i < len; ++i) {
            lastFour += str[i];
        }
        std::cout << "Last 4 characters: " << lastFour << std::endl;
    } else {
        std::cout << "String is too short to extract 4 characters." << std::endl;
    }

    return 0;
}

方法三：使用`rbegin`和`rend`

#include <iostream>
#include <string>

int main() {
    std::string str = "Hello, World!";
    int len = str.length();
    std::string lastFour = "";

    if (len >= 4) {
        for (auto it = str.rbegin(); it != str.rbegin() + 4; ++it) {
            lastFour = *it + lastFour;
        }
        std::cout << "Last 4 characters: " << lastFour << std::endl;
    } else {
        std::cout << "String is too short to extract 4 characters." << std::endl;
    }

    return 0;
}