c++如何使用STL中的算法_c++ STL标准算法库应用实战

std::vector

std::list

std::map

#include <iostream>
#include <vector>
#include <algorithm> // for std::sort, std::find, std::for_each
#include <numeric>   // for std::accumulate
#include <list>      // for std::list

int main() {
    std::vector<int> numbers = {5, 2, 8, 1, 9, 3};

    // 1. 排序：使用std::sort对vector进行升序排序
    std::sort(numbers.begin(), numbers.end());
    std::cout << "Sorted vector: ";
    for (int n : numbers) {
        std::cout << n << " ";
    }
    std::cout << std::endl; // Output: 1 2 3 5 8 9

    // 2. 查找：使用std::find查找特定元素
    auto it = std::find(numbers.begin(), numbers.end(), 8);
    if (it != numbers.end()) {
        std::cout << "Found 8 at index: " << std::distance(numbers.begin(), it) << std::endl;
    } else {
        std::cout << "8 not found." << std::endl;
    }

    // 3. 遍历并修改：使用std::transform将所有元素加1
    std::vector<int> transformed_numbers(numbers.size()); // 需要一个目标容器
    std::transform(numbers.begin(), numbers.end(), transformed_numbers.begin(),
                   [](int x) { return x + 1; });
    std::cout << "Transformed vector (each +1): ";
    for (int n : transformed_numbers) {
        std::cout << n << " ";
    }
    std::cout << std::endl; // Output: 2 3 4 6 9 10

    // 4. 累加：使用std::accumulate计算所有元素的和
    int sum = std::accumulate(numbers.begin(), numbers.end(), 0); // 0是初始值
    std::cout << "Sum of numbers: " << sum << std::endl; // Output: 28

    // 5. 使用std::for_each打印元素 (或Lambda直接处理)
    std::cout << "Elements printed with for_each: ";
    std::for_each(numbers.begin(), numbers.end(), [](int n) {
        std::cout << n << "* ";
    });
    std::cout << std::endl; // Output: 1* 2* 3* 5* 8* 9*

    // 6. 条件删除：std::remove_if 结合 erase
    // 注意：std::remove_if 不会改变容器大小，它只是将不满足条件的元素移动到前面，
    // 并返回一个指向新逻辑末尾的迭代器。需要结合容器的 erase 成员函数来真正删除。
    std::vector<int> data = {1, 5, 2, 8, 3, 5, 9, 4};
    auto new_end = std::remove_if(data.begin(), data.end(), [](int val) {
        return val == 5; // 删除所有值为5的元素
    });
    data.erase(new_end, data.end()); // 真正从容器中移除
    std::cout << "Vector after removing 5s: ";
    for (int n : data) {
        std::cout << n << " ";
    }
    std::cout << std::endl; // Output: 1 2 8 3 9 4

    return 0;
}

std::sort

std::sort(vec.begin(), vec.end())

vec

std::find

vector

list

deque

for

std::vector<Person>

Person

name

age

for

[] (params) -> return_type { body }

vector<SensorData>

value

struct SensorData {
    long timestamp;
    double value;
    // ...
};

// ...
std::vector<SensorData> all_data = /* ... */;
long start_time = 1678886400; // 某个起始时间
long end_time = 1678887000;   // 某个结束时间
double threshold = 100.0;

// 找出满足条件的所有数据，并放入一个新的vector
std::vector<SensorData> filtered_data;
std::copy_if(all_data.begin(), all_data.end(), std::back_inserter(filtered_data),
             [start_time, end_time, threshold](const SensorData& sd) {
                 return sd.timestamp >= start_time &&
                        sd.timestamp <= end_time &&
                        sd.value > threshold;
             });

[start_time, end_time, threshold](const SensorData& sd) { ... }

operator()

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

class NthElementProcessor {
private:
    int n_;
    int count_;
public:
    NthElementProcessor(int n) : n_(n), count_(0) {}

    void operator()(int val) {
        if (++count_ % n_ == 0) {
            std::cout << "Processing " << n_ << "th element: " << val << std::endl;
        }
    }
};

int main() {
    std::vector<int> data = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // 使用函数对象处理每隔3个元素
    std::for_each(data.begin(), data.end(), NthElementProcessor(3));
    // Output:
    // Processing 3th element: 3
    // Processing 3th element: 6
    // Processing 3th element: 9

    // 另一个例子：统计偶数个数
    class EvenCounter {
    private:
        int even_count_ = 0;
    public:
        void operator()(int val) {
            if (val % 2 == 0) {
                even_count_++;
            }
        }
        int get_count() const { return even_count_; }
    };

    EvenCounter counter;
    std::for_each(data.begin(), data.end(), std::ref(counter)); // 注意这里用std::ref传递引用
    std::cout << "Number of even elements: " << counter.get_count() << std::endl; // Output: 5

    return 0;
}

EvenCounter

counter