单位化局部变量和帮助纠正 [英] Unitialized local variable and help correcting
问题描述
我正在学习指针和类中的 new 运算符。
在我的readArray函数中，读取大小。使用大小动态创建整数数组。然后将数组赋给一个指针，填充它，并返回大小和数组。
我相信我已经纠正和修正了这部分，但是当我尝试排序数组，我得到错误未初始化的局部变量 temp 。
问题是，虽然我得到那个错误，当我试图初步化它。
任何帮助谢谢谢谢。看到我的错误对我非常有帮助。
#include< iostream&
using namespace std;
int * readArray（int&）;
void sortArray（int *，const int *）;
int main（）
{
int size = 0;
int * arrPTR = readArray（size）;
const int * sizePTR =& size;
sortArray（arrPTR，sizePTR）;
cout<< arrPTR [1]<< arrPTR [2]<< arrPTR [3]<< arrPTR [4]
系统（pause）;
return 0;
}
int * readArray（int& size）
{
cout<<输入一个数组大小的数字。 n。
cin>> size;
int * arrPTR = new int [size];
for（int count = 0; count<（size-1）; count ++）
{
cout<<输入正数以完全填充数组。 \\ n;
cin>> *（arrPTR + count）;
}
return arrPTR;
}
void sortArray（int * arrPTR，const int * sizePTR）
{
int * temp;
bool * swap;
do
{
swap = false;
for（int count = 0; count <（* sizePTR-1）; count ++）
{
if（arrPTR [count]> arrPTR [count + 1]）$ b $ b {
* temp = arrPTR [count];
arrPTR [count] = arrPTR [count + 1];
arrPTR [count + 1] = * temp;
* swap = true;
}
}
} while（swap）;
}
c> temp 作为指针。您需要在解除引用之前在堆上分配它，并在稍后分配给它。
FYI：你应该注意 readArray
#include< iostream>
int * readArray（int&）;
void sortArray（int *，int）;
int main（）
{
int size（0）; //可能时使用堆栈
int * arrPTR = readArray（size）;
sortArray（arrPTR，size）;
//数组是基于零的索引从0到大小
for（int index（0）; index< size; ++ index）
std :: cout << arrPTR [index];
delete [] arrPTR; //记得删除数组或者我们有一个内存泄漏！
//注意：因为我们为一个数组做了新的[]，我们将它与delete []匹配
//如果我们刚刚做了新的，我们就可以用delete
（暂停）;
return 0;
}
int * readArray（int& size）
{
std :: cout< 输入数组大小的数字。\\\
;
std :: cin>>尺寸;
int * arrPTR = new int [size]; //所有新闻必须删除！
//喜欢预递增到后递增，你可以
为（int count（0）; count< size; ++ count）
{
std :: cout<< 输入正数以完全填充数组。
std :: cin>> arrPTR [count];
}
返回arrPTR;
}
//通过值传递大小（可能小于某些架构上的指针）
void sortArray（int * arrPTR，int size）
{
//你可能想检查大小> = 2是否为sanity
//我们做两个循环，以避免在上次迭代时超出数组的边界
for（int i（0）; i
for（int j（i + 1）; j < size; ++ j）//第二比较（除了第一个）
{
//比较
if（arrPTR [i]> arrPTR [j] /从最小到最大（使用<从最大到最小）
{
//如果需要，交换
int temp（arrPTR [i]）; // put this on stack
arrPTR [i] = arrPTR [j];
arrPTR [j] = temp;
}
}
}
}
I am learning about pointers and the new operator in class.
In my readArray function I am to read in a size. Use the size to dynamically create an integer array. Then assign the array to a pointer, fill it, and return the size and array.
I believe I've gotten that part corrected and fixed but when I try to sort the array, i get the error "uninitialized local variable temp used."
The problem is though I get that error when I am trying to intialize it. Any help appreciated thank you. Seeing my errors is very helpful for me.
#include <iostream>
using namespace std;
int* readArray(int&);
void sortArray(int *, const int * );
int main ()
{
int size = 0;
int *arrPTR = readArray(size);
const int *sizePTR = &size;
sortArray(arrPTR, sizePTR);
cout<<arrPTR[1]<<arrPTR[2]<<arrPTR[3]<<arrPTR[4];
system("pause");
return 0;
}
int* readArray(int &size)
{
cout<<"Enter a number for size of array.\n";
cin>>size;
int *arrPTR = new int[size];
for(int count = 0; count < (size-1); count++)
{
cout<<"Enter positive numbers to completely fill the array.\n";
cin>>*(arrPTR+count);
}
return arrPTR;
}
void sortArray(int *arrPTR, const int *sizePTR)
{
int *temp;
bool *swap;
do
{
swap = false;
for(int count = 0; count < (*sizePTR - 1); count++)
{
if(arrPTR[count] > arrPTR[count+1])
{
*temp = arrPTR[count];
arrPTR[count] = arrPTR[count+1];
arrPTR[count+1] = *temp;
*swap = true;
}
}
}while (swap);
}
You declared temp as a pointer. You need to allocate it on the heap before dereferencing and assigning to it later. However perhaps a variable on the stack would be preferable?
FYI: You should be aware of the memory leak in readArray as well which is leaving callers responsible for calling delete []
Edit: I hope this will help clear up some of the other problems.
#include <iostream>
int* readArray(int&);
void sortArray(int*, int);
int main ()
{
int size(0); // use stack when possible
int *arrPTR = readArray(size);
sortArray(arrPTR, size);
// arrays are zero based index so loop from 0 to size
for (int index(0); index < size; ++index)
std::cout << arrPTR[index];
delete [] arrPTR; // remember to delete array or we have a memory leak!
// note: because we did new[] for an array we match it with delete[]
// if we just did new we would match it with delete
system("pause");
return 0;
}
int* readArray(int& size)
{
std::cout << "Enter a number for size of array.\n";
std::cin >> size;
int *arrPTR = new int[size]; // all news must be deleted!
// prefer pre-increment to post-increment where you can
for(int count(0); count < size; ++count)
{
std::cout << "Enter positive numbers to completely fill the array.\n";
std::cin >> arrPTR[count];
}
return arrPTR;
}
// passing size by value is fine (it may be smaller than pointer on some architectures)
void sortArray(int *arrPTR, int size)
{
// you may want to check if size >= 2 for sanity
// we do the two loops to avoid going out of bounds of array on last iteration
for(int i(0); i < size-1; ++i) // the first to compare (all except last)
{
for(int j(i+1); j < size; ++j) // the second to compare (all except first)
{
// do comparison
if (arrPTR[i] > arrPTR[j]) // from smallest to biggest (use < to go from biggest to smallest)
{
// swap if needed
int temp(arrPTR[i]); // put this on stack
arrPTR[i] = arrPTR[j];
arrPTR[j] = temp;
}
}
}
}
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