[英]send dynamic array of pointer to function in c++
I trying to send array to function, but my program gets stuck 我试图将数组发送给函数,但是我的程序被卡住了
int main()
{
int n, i;
bool random;
cout << "number of elements in array:"; cin >> n;
cout << "use random values?"; cin >> random;
int* arr = new int[n]; //create int array with n size
init_array(random, n, arr); //fill array using function
for (i = 0; i <= n; i++) //display array
cout << " " << arr[i];
return 0;
}
This function should fill array with random number or input from keyboard 此函数应使用随机数或键盘输入来填充数组
void init_array(bool random, int n, int* arr)
{
int i;
if (random)
{
srand(time(0)); //initialize random;
for (i = 0; i < n; i++)
arr[i] = rand() % 100;
}
else
for (i = 0; i<n; i++)
cout << "arr[" << i << "]: "; cin >> arr[i];
}
Is there any way send dynamic array to function? 有什么办法可以发送动态数组来起作用吗?
When you do not use brackets after your for-loop, only the first statement is used as a loop: 如果在for循环后不使用方括号,则仅将第一条语句用作循环:
else
for (i = 0; i<n; i++)
cout << "arr[" << i << "]: "; cin >> arr[i];
This loop will attempt to print "arr[#]" n
times, and then ask for an input (which will attempt to be placed in the item 1 after the last element in your array (UB). 此循环将尝试打印n
次“ arr [#]”,然后要求输入(它将尝试放置在数组(UB)中最后一个元素之后的第1项中)。
What you want is this: 您想要的是:
else
{
for (i = 0; i<n; i++)
{
cout << "arr[" << i << "]: ";
cin >> arr[i];
}
}
You also have a problem with your output: 您的输出也有问题:
for (i = 0; i < n; i++) // <= would attempt to print 1 more item than exists in the array
And just for completeness, most of these issues go away when you use a container that does all of this for you: 仅出于完整性考虑,当您使用为您完成所有这些工作的容器时,这些问题中的大多数都会消失:
int main()
{
int n = 0;
bool useRandom = false;
std::cout << "number of elements in array:";
std::cin >> n;
std::cout << "use random values?";
std::cin >> useRandom;
std::vector<int> arr(n);
init_array(useRandom, arr);
std::copy(arr.begin(), arr.end(), std::ostream_iterator<int>(std::cout, " "));
return 0;
}
void init_array(bool useRandom, std::vector<int>& vec)
{
::srand(time(0)); //initialize random;
int n = 0;
std::transform(vec.begin(), vec.end(), vec.begin(), [&](int i)
{
if (useRandom)
{
i = rand() % 100;
}
else
{
std::cout << "arr[" << n++ << "]: ";
std::cin >> i;
}
return i;
});
}
Your code is asking for a number at the end because of last cin>>n
您的代码要求最后输入一个数字,因为最后一个cin>>n
fix else
part in init_array
as: 将init_array
else
部分修复为:
else
for (i = 0; i<n; i++)
{ //Notice braces
cout << "arr[" << i << "]: ";
cin >> arr[i];
}
Also fix: 同时解决:
for (i = 0; i < n; i++) //display array from index 0 to n-1
cout << " " << arr[i];
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