将Vector元素复制到动态数组中 [英] copying Vector elements into Dynamic Array
问题描述
/ * C ++入门 - 4 / e
*第4章阵列&指针，练习4.28
*语句
*编写一个程序来读取标准输入并构建一个向量
的整数来自读取的值。分配一个相同的
大小的数组作为向量并将向量中的元素复制到数组中
* /
#include< iostream>
#include< vector>
int main（）
{
int iv;
std :: vector< intivec;
while（std :: cin> iv）
{
ivec.push_back（iv）;
}
const size_t arr_sz = ivec.size（） + 1;
int * pdarr = new int [arr_sz];
int * pbegin = pdarr;
/ *我们将使用" pbegin"以后打印数组元素* /
/ *将向量中的元素分配给动态数组* /
for（std :: vector< int>： ：const_iterator iter = ivec.begin（）;
iter！= ivec.end（）; ++ iter）
{
* pdarr ++ = * iter;
}
/ *打印arrar元素* /
std :: cout<< 打印数组元素：" ;;
for（int * q = pbegin; q！= pbegin + arr_sz; ++ q）
{
std :: cout<< * q<< " " ;;
}
std :: cout<< std :: endl;
返回0;
}
========输出===========
~ / programming / cpp $ g ++ -ansi -pedantic -Wall -Wextra ex_04-28.cpp
~ / programming / cpp $ ./a.out
2
3
-9
8
打印数组元素：2 3 -9 8 0
~ / programming / cpp $
i有2个问题：
1.）我使用了vecotor size + 1。对于数组大小，但我没有输入最后的
字符为NULL。该程序是否将它自动添加到数组末尾
？
2.）输出最后包含一个额外的整数，零，0。我不是因为我使用了q！=
pbegin + arr_size而让指针滑落到数组的末尾。那么零来自哪里？
-
- http://arnuld.blogspot.com
/* C++ Primer - 4/e
* chapter 4- Arrays & Pointers, exercise 4.28
* STATEMENT
* write a programme to read the standard input and build a vector
of integers from values that are read. allocate an array of the same
size as the vector and copy elements from the vector into the array
*/
#include <iostream>
#include <vector>
int main()
{
int iv;
std::vector<intivec;
while(std::cin >iv)
{
ivec.push_back(iv);
}
const size_t arr_sz = ivec.size() + 1;
int* pdarr = new int[arr_sz];
int* pbegin = pdarr;
/* we will use "pbegin" to print the array elements later */
/* assign elements from vector to the dynamic array */
for(std::vector<int>::const_iterator iter=ivec.begin();
iter != ivec.end(); ++iter)
{
*pdarr++ = *iter;
}
/* printing the elements of arrar */
std::cout << "printing array elements: ";
for(int* q = pbegin; q != pbegin + arr_sz; ++q)
{
std::cout << *q << " ";
}
std::cout << std::endl;
return 0;
}
======== OUTPUT ===========
~/programming/cpp $ g++ -ansi -pedantic -Wall -Wextra ex_04-28.cpp
~/programming/cpp $ ./a.out
2
3
-9
8
printing array elements: 2 3 -9 8 0
~/programming/cpp $
i have 2 questions:
1.) i have used "vecotor size + 1" for array size but i did not enter last
character as NULL. does the programme add it to the end of array itself
automatically ?
2.) output contains an extra integer in the end, the zero, 0. i am not
letting the pointer slipping-off the end of array because i used "q !=
pbegin + arr_size" then from where the zero came ?
--
-- http://arnuld.blogspot.com
推荐答案
g ++ -ansi -pedantic -Wall -Wextra ex_04-28.cpp
~ / programming / cpp
g++ -ansi -pedantic -Wall -Wextra ex_04-28.cpp
~/programming/cpp
./ a.out
2
3
-9
8
打印数组元素：2 3 -9 8 0
~ /编程/ cpp
./a.out
2
3
-9
8
printing array elements: 2 3 -9 8 0
~/programming/cpp
i有两个问题：
1.）我使用了vecotor size + 1对于数组大小，但我没有输入最后的
字符为NULL。该程序是否将它自动添加到数组末尾
？
2.）输出最后包含一个额外的整数，零，0。我不是因为我使用了q！=
pbegin + arr_size而让指针滑落到数组的末尾。那么零来自哪里？
-
- http://arnuld.blogspot.com
i have 2 questions:
1.) i have used "vecotor size + 1" for array size but i did not enter last
character as NULL. does the programme add it to the end of array itself
automatically ?
2.) output contains an extra integer in the end, the zero, 0. i am not
letting the pointer slipping-off the end of array because i used "q !=
pbegin + arr_size" then from where the zero came ?
--
-- http://arnuld.blogspot.com
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