std::erase总结

Posted 2020-12-22 foreversdf

std::erase：

（1）string& erase ( size_t pos = 0, size_t n = npos );

    std::string test = "Hello erase!";
    test.erase(2, 6);
    //test.erase(2);
    //删除指定字符串
    //test.erase(test.find("llo"), 3);
    std::cout << "test: " << test.c_str() << std::endl;

【输出】

• Hease!
• He
• He erase!

（2）iterator erase ( iterator position );

    std::string test = "Hello erase!";
    test.erase(test.begin());
    //test.erase(test.begin() + 1);
    //test.erase(test.end() - 1);
    //删除指定字符
    //test.erase(find(test.begin(), test.end(), ‘l‘));
    std::cout << "test: " << test.c_str() << std::endl;

【输出】

• ello erase!
• Hllo erase!
• Hello erase
• Helo erase!

（3）iterator erase ( iterator first, iterator last );

    std::string test = "Hello erase!";
    test.erase(test.begin(), test.begin() + 4);
    //test.erase(test.begin(), test.end() - 1);
    std::cout << "test: " << test.c_str() << std::endl;

【输出】

• o erase!
• !

（4）some feature and warning

• 搭配remove_if和lambda表达式

    std::vector<int> c{ 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int x = 5;
    c.erase(std::remove_if(c.begin(), c.end(), [x](int n) { return n < x; }), c.end());
    std::cout << "c: ";
    for (auto i : c) {
        std::cout << i << ", ";
    }

【输出】c: 5, 6, 7, 8, 9

• 注意迭代器失效问题

    std::vector<int> c{ 1, 2, 3, 4, 5, 6, 6, 6, 6, 7, 8, 9 };
    //erase后it迭代器成为了野指针，这里指向了下一个指针。错误写法
    for (auto it = c.begin(); it != c.end(); it++) {
        if (*it == 6) {
            c.erase(it);
        }
    }
    //正确写法
    auto it = c.begin();
    while (it != c.end()) {
        if (*it == 6) {
            it = c.erase(it);
        }
        else {
            it++;
        }
    }
    std::cout << "c: ";
    for (auto i : c) {
        std::cout << i << ", ";
    }

【输出】c: 1, 2, 3, 4, 5, 7, 8, 9