Essential C++ 3.1 节的代码练习——指针方式

//
//  PointerToValue.cpp
//  Working
//
//  Created by Hawkins, Dakota Y on 6/3/16.
//  Copyright  2016 Hawkins, Dakota Y. All rights reserved.
//

#include "PointerToValue.hpp"
#include <cstdio>
#include <vector>
#include <iostream>

using namespace std;



template <typename element> 
element *find_value(vector<element> &vec, element value)
{
    for (int i = 0; i < vec.size(); i++)
    {
        if (vec[i] == value)
        {
            return &vec[i];
        }
    }
    return 0;
}




template <typename T> 
T *find_value(T *array, int size, T value)
{
    if (! array || size < 1)
    {
        return 0;
    }
    for (int i = 0; i < size; i++)
    {
        if (array[i] == value)
        {
            return &array[i];
        }
    }
    return 0;
}


template <typename element>
int find_pos(vector<element> &vec, element value)
{
    int pos_val;
    for (int i = 0; i < vec.size(); i++)
    {
        if (vec[i] == value)
        {
            pos_val = i;
            return pos_val;
        }
    }
    return 0;
}

int main()
{
    int int_array[5] = {13, 3, 34, 42, 53};
    string str_array[5] = {"Hello", ",", "how", "are", "you?"};
    float float_array[5] = {0.123, 4.5, 10.1, 5.7, 10};

    vector<int> int_vector(int_array, int_array + 5);
    vector<string> str_vector(str_array, str_array + 5);
    vector<float> float_vector(float_array, float_array + 5);

    cout << "pos of 3 = " << find_pos(int_vector,53) <<endl;

    cout << "Pointer of '3' in 'int_vector': " << find_value(int_vector, 3) << endl;
    //cout <<*(find_value(int_vector, 3))<<endl;    //cout the value of 3

    cout << "Pointer of 'Hello' in 'str_vector': " << find_value(str_vector, string("Hello")) << endl;

    float f_test = 11.1;
    cout << "Pointer of '11.1' in 'float_vector': " << find_value(float_vector, f_test) << endl;

    float first_value = float_array[1];
    cout << "Pointer of 4.5 in 'float_array': " << find_value(&first_value, int(5), float(4.5)) << endl;
    return 0;
}

输出：

pos of 3 = 4

Pointer of '3' in 'int_vector': 0x1c1554

Pointer of 'Hello' in 'str_vector': 0x1c1a50

Pointer of '11.1' in 'float_vector': 0

Pointer of 4.5 in 'float_array': 0x73fc8c