C++ - 泛型指针使用示例

原创已于 2022-10-23 15:48:12 修改 · 637 阅读

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于 2022-10-19 16:09:03 首次发布

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这篇博客展示了如何使用C++模板函数实现`find`和`find_pre_version`两个查找算法，并在整型数组、双精度浮点型数组和字符串数组中应用。示例代码包括对`vector`和`list`容器的查找操作，最后运行结果验证了算法的正确性。

等后面学完了再来细写，先备份个代码。
参考：

《Essential C++》

#include <iostream>
#include <vector>
#include <list>
using namespace std;

template <typename elemType>
elemType *find_pre_version(const elemType *array, const elemType *sentinel, const elemType &value);
// const情况会导致传入string指针时报错

template <typename IteratorType, typename elemType>
IteratorType find(IteratorType first, IteratorType last, const elemType &value)
{
    for (; first != last; ++first)
    {
        if (*first == value)
        {
            return first;
        }
    }
    return last;
}

template <typename elemType>
elemType *find_pre_version(elemType *first,elemType *last, const elemType &value)
{
    if (!first || !last)
    {
        return 0;
    }
    for (; first != last; ++first)
    {
        if (*first == value)
        {
            return first;
        }
    }
    return 0;
}


template <typename elemType>
inline elemType *begin(vector<elemType> &vec)
{
    return vec.empty() ? 0 : &vec[0];
}

template <typename elemType>
inline elemType *end(vector<elemType> &vec)
{
    return vec.empty() ? 0 : &vec[vec.size()];
}

int main()
{
    int ia[8] = {1, 2, 3, 4, 5, 6, 7, 8};
    double da[8] = {1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5};
    string sa[8] = {"a0", "b1", "c2", "d3", "e4", "f5", "g6", "h7"};
    int *pi = find(ia, ia + 8, ia[3]);
    double *pd = find(da, da + 8, da[3]);
    string *ps = find(sa, sa + 8, sa[3]);
    cout << "*pi: " << *pi << ", *pd: " << *pd << ", *ps: " << *ps << endl;

    vector<int> via(ia, ia + 8);
    vector<int>::iterator it;
    it = find(via.begin(), via.end(), 5);
    if(it != via.end()) {
        cout << "*vector_iter: " << *it << endl;
    }
    
    int *vpi = find_pre_version(begin<int>(via), end<int>(via), 5);
    cout << "*vpi: " << *vpi << endl;

    list<int> lia(ia, ia+8);
    list<int>::iterator iter;
    iter = find(lia.begin(), lia.end(), 5);
    if(iter != lia.end()) {
        cout << "*list_iter: " << *iter << endl;
    }

    return 0;
}

输出结果：

*pi: 4, *pd: 2.5, *ps: d3
*vector_iter: 5
*vpi: 5
*list_iter: 5