C++如何使用STL算法实现元素转换

std::transform

std::transform

std::transform

std::vector<int>

#include <vector>
#include <algorithm>
#include <iostream>
#include <numeric> // 为了std::iota，方便填充数据

int main() {
    std::vector<int> original_numbers(5);
    std::iota(original_numbers.begin(), original_numbers.end(), 1); // 填充1, 2, 3, 4, 5

    std::vector<int> squared_numbers(original_numbers.size());

    // 使用lambda表达式进行平方转换
    std::transform(original_numbers.begin(), original_numbers.end(),
                   squared_numbers.begin(),
                   [](int n) { return n * n; });

    std::cout << "Original numbers: ";
    for (int n : original_numbers) {
        std::cout << n << " ";
    }
    std::cout << std::endl;

    std::cout << "Squared numbers: ";
    for (int n : squared_numbers) {
        std::cout << n << " ";
    }
    std::cout << std::endl;

    // 也可以原地转换，如果输出范围和输入范围相同，但要注意原地修改的副作用
    std::vector<int> numbers_to_double = {10, 20, 30};
    std::transform(numbers_to_double.begin(), numbers_to_double.end(),
                   numbers_to_double.begin(), // 输出到原位置
                   [](int n) { return n * 2; });

    std::cout << "Doubled numbers (in-place): ";
    for (int n : numbers_to_double) {
        std::cout << n << " ";
    }
    std::cout << std::endl;

    return 0;
}

#include <vector>
#include <algorithm>
#include <iostream>
#include <numeric>

int main() {
    std::vector<int> vec1 = {1, 2, 3};
    std::vector<int> vec2 = {4, 5, 6};
    std::vector<int> sum_vec(vec1.size()); // 确保输出容器有足够空间

    // 使用lambda表达式进行元素相加
    std::transform(vec1.begin(), vec1.end(),
                   vec2.begin(), // 第二个输入范围的开始
                   sum_vec.begin(), // 输出范围的开始
                   [](int a, int b) { return a + b; });

    std::cout << "Vector 1: ";
    for (int n : vec1) std::cout << n << " ";
    std::cout << std::endl;

    std::cout << "Vector 2: ";
    for (int n : vec2) std::cout << n << " ";
    std::cout << std::endl;

    std::cout << "Sum vector: ";
    for (int n : sum_vec) std::cout << n << " ";
    std::cout << std::endl;

    return 0;
}

std::transform

int

double

std::transform

std::vector<Person>

Person

name

age

Person

std::vector<std::string>

"Name: [name], Age: [age]"

std::transform

#include <vector>
#include <algorithm>
#include <iostream>
#include <string>
#include <iterator> // For std::back_inserter

struct Person {
    std::string name;
    int age;
    // 构造函数方便初始化
    Person(std::string n, int a) : name(std::move(n)), age(a) {}
};

int main() {
    std::vector<Person> people = {
        {"Alice", 30},
        {"Bob", 24},
        {"Charlie", 35}
    };

    std::vector<std::string> person_descriptions;
    // 预留空间是个好习惯，避免多次重新分配，但这里使用back_inserter可以省略
    // person_descriptions.reserve(people.size