recursion

问题 This excellent answer to Return a list of all objects vertically stacked above a given object? started me on tree traversal, now I need to start building a complex control panel using wxPython. I'm learning about sizers but for this abstracted script I've used matplotlib to generate what the panel will look like. The part I need help with is only the bit near the end with the comments First layer , Second layer and Third layer . What I need is to use recursion so that I don't have to have the

问题 If I have a string 4+6*7/2 I want a function which calculates the value, in this case 25. To achieve this I have written a recursive function which analyses the string character by character. The basic algorithm goes (or should go) like this: If the character we analyse now is a normal cipher and we haven't encountered an operator (+, -, *, /) yet we store it in a string called first_nr , which will eventually become the number on the left side of the operator. This we do until we encounter

问题 Assuming a simplified football scoring system where you can score {2, 3, 7} points, what are all the possible ways that you can score given a number of points? I'm just working problems in the EPI book, and he solves this problem using DP. I wanted to practice a recursive technique, but I'm getting tripped up trying to save all the different ways in to a results list. def find_scoring(points, scores): ways_to_score = [2, 3, 7] def score_finder(p, scores): print(scores, p) if p == 0: print(

问题 Assuming a simplified football scoring system where you can score {2, 3, 7} points, what are all the possible ways that you can score given a number of points? I'm just working problems in the EPI book, and he solves this problem using DP. I wanted to practice a recursive technique, but I'm getting tripped up trying to save all the different ways in to a results list. def find_scoring(points, scores): ways_to_score = [2, 3, 7] def score_finder(p, scores): print(scores, p) if p == 0: print(

问题 I am growing a 2D array by it's column and row size in c programming. #include <stdio.h> #include <malloc.h> //#include <conio.h> //#include <stdlib.h> void func(int** p, int d, int** sizes) { static int count = 0; int* item = NULL; int* temp = NULL; if (d == 5) return; *sizes = (int*) realloc(*sizes, (d + 1) * sizeof(*sizes)); *sizes[count] = d + 1; // <=== in second recursive call it throws memory allocation errors here in runtime //p = (int**) realloc(p, (count + 1) * sizeof(int*)); /

问题 Using boost::spirit, if I have a recursive rule to parse parentheses rule<std::string::iterator, std::string()> term; term %= string("(") >> *term >> string(")"); how do I limit the maximum amount of recursion? For example, if I try to parse a million nested parentheses, I get a segfault because the stack size has been exceeded. To be concrete, here is a complete sample. #include <iostream> #include <string> #include <boost/spirit/include/qi.hpp> int main(void) { using namespace boost::spirit

问题 Using boost::spirit, if I have a recursive rule to parse parentheses rule<std::string::iterator, std::string()> term; term %= string("(") >> *term >> string(")"); how do I limit the maximum amount of recursion? For example, if I try to parse a million nested parentheses, I get a segfault because the stack size has been exceeded. To be concrete, here is a complete sample. #include <iostream> #include <string> #include <boost/spirit/include/qi.hpp> int main(void) { using namespace boost::spirit

问题 template <typename T> T sum(stack<T>& s){ if (s.empty()){ return 0; } else { T first = s.top(); s.pop(); T total = sum(s)+first; s.push(first); return total; } } The code above is designed to recursively sum the elements of any given stack of type T with the only condition being that the integrity of the stack must be restored at the end of the function. Meaning, I am allowed to make changes to the stack to sum the elements as long as it is in the same state as it was before it was passed

问题 Given a recursive function in scheme how do I change that function to tail recursive, and then how would I implement it using streams? Are there patterns and rules that you follow when changing any function in this way? Take this function as an example which creates a list of numbers from 2-m (this is not tail recursive?) Code: (define listupto (lambda (m) (if (= m 2) '(2) (append (listupto (- m 1)) (list m))))) 回答1: I'll start off by explaining your example. It is definitely not tail

问题 Why does the following code cause a StackOverflowException in .Net4.8 with only a 17-depth recursion? However this does not happen in NetCore 3.1 (I can set the count to 10_000 and it still works) class Program { static async Task Main(string[] args) { try { await TestAsync(17); } catch(Exception e) { Console.WriteLine("Exception caught: " + e); } } static async Task TestAsync(int count) { await Task.Run(() => { if (count <= 0) throw new Exception("ex"); }); Console.WriteLine(count); await