function-definition

问题 This question already has answers here : What does -> mean in Python function definitions? (8 answers) Closed 2 years ago . I have found the following python function definition: def reverseString(self, s: 'List[str]') -> 'None': I don't quite understand 'List[str]' and -> 'None' . I have found that the arrow is a function annotation but I couldn't find anything useful and understandable for List[str]. Is it just an annotation? or does it enforce that the type of parameter s must be a string

问题 #include<stdio.h> void swap(int *a,int *b){ int p=*b; *b=*a; *a=p; /*int *p=b; b=a; a=p; */ } int main(){ int a,b; scanf("%d %d",&a,&b); swap(&a,&b); printf("%d %d",a,b); } Above is the code. If I put 3 5 as an input, then it should swap its values, and 5 3 should come out as an output. I got my answer by trying int p=*b thing However I also tried commented part, but it didn't work. So, I checked their address in swap and in main. In swap int *a and int *b their address changed However, when

问题 I read that the extern keyword is implicit in the context of functions, so unless you specify otherwise using the static keyword ( which if I'm not mistaken is basically a completely separate concept from the static that variables employ—they just share a keyword ), they are visible to all object files. This makes sense; having the declarations be implicitly external, while technically unnecessary when the declarations are in the same file as the definition, is useful because the programmer

问题 I read that the extern keyword is implicit in the context of functions, so unless you specify otherwise using the static keyword ( which if I'm not mistaken is basically a completely separate concept from the static that variables employ—they just share a keyword ), they are visible to all object files. This makes sense; having the declarations be implicitly external, while technically unnecessary when the declarations are in the same file as the definition, is useful because the programmer

问题 How can i find only the elements that appears once in the list and return the cardinal number?For example if my list consist of {3,2,1,1,2,4} i expect for return the counter to be 4 and not 6 cause we do not count the duplicate numbers. Here is the code that i have written so far. struct Node { int data; struct Node *next; }; int Find_cardinal(struct Node *start) { struct Node *ptr1, *ptr2 ptr1 = start; int counter=0; /* Pick elements one by one */ while (ptr1 != NULL && ptr1->next != NULL) {

问题 I'm trying to declare a pointer and pass that pointer to a function where memory is allocated. Here is a minimal example: #include <string> #include <iostream> using namespace std; void alloc_mem(int &size, double *x); int main() { double *X; int imax; alloc_mem(imax, X); cout << "imax = " << imax << endl; for (int i = 0; i < imax; i++) { cout << "X = " << X[i] << endl; } delete[]X; return 0; } void alloc_mem(int &size, double *x) { size = 10; x = new double[size]; for (int i = 0; i < size; i

问题 I'm trying to declare a pointer and pass that pointer to a function where memory is allocated. Here is a minimal example: #include <string> #include <iostream> using namespace std; void alloc_mem(int &size, double *x); int main() { double *X; int imax; alloc_mem(imax, X); cout << "imax = " << imax << endl; for (int i = 0; i < imax; i++) { cout << "X = " << X[i] << endl; } delete[]X; return 0; } void alloc_mem(int &size, double *x) { size = 10; x = new double[size]; for (int i = 0; i < size; i

问题 E.g., I have an empty function to clear a linked list: void empty(Node* head) { if (head->next) { empty(head->next); } delete head; head = nullptr; } But then I created a class for the linked list, so now I don't need to pass the head argument: void empty() { if (head->next) { empty(head->next); } delete head; head = nullptr; } But empty(head->next) line is obviously wrong as empty doesn't take any arguments. The idea comes to my mind to create a function inside a function (with lambda),

问题 I need an interface that would require its subclasses to overload << and >> , but I'm not quite sure how since these operators aren't overloaded as member functions: std::istream& operator>> (std::istream& in, Student& student) { in >> student.name >> student.group; for (int& i : student.marks) { in >> i; } return in; } Maybe there's a way to make it a member function? 回答1: You could do something like this: class StudentInterface { public: virtual void readSelfFrom(std::istream& in) = 0; };

问题 How can I know whether to use def, cdef or cpdef when defining a Cython function, assuming I want optimal performance? 回答1: If you want optimal performance, you should know that as mentioned in this answer to a related question: Once the function has been called there is no difference in the speed that the code inside a cdef and a def function runs at. So for optimal Cython performance you should always statically type all arguments and variables , and intuitively you would then be tempted to