recursion

问题 Here is my question I am trying to create a random bar code for my application, I want to check if that code is already in the column than generate a new number, check it again if its unique return it to the caller else generate again. I am using a recursive function for this purpose. I have added number 1,2,3,4 inside my database so every time it runs it has to show me 5,6,7,8,9 or 10. Here is my function: function generate_barcode(){ $barcode = rand(1,10); $bquery = mysql_num_rows(mysql

问题 Here is my question I am trying to create a random bar code for my application, I want to check if that code is already in the column than generate a new number, check it again if its unique return it to the caller else generate again. I am using a recursive function for this purpose. I have added number 1,2,3,4 inside my database so every time it runs it has to show me 5,6,7,8,9 or 10. Here is my function: function generate_barcode(){ $barcode = rand(1,10); $bquery = mysql_num_rows(mysql

问题 Is this function tail-recursive ? let rec rec_algo1 step J = if step = dSs then J else let a = Array.init (Array2D.length1 M) (fun i -> minby1J i M J) let argmin = a|> Array.minBy snd |> fst rec_algo1 (step+1) (argmin::J) In general, is there a way to formally check it ? Thanks. 回答1: This function is tail-recursive; I can tell by eyeballing it. In general it is not always easy to tell. Perhaps the most reliable/pragmatic thing is just to check it on a large input (and make sure you are

问题 #include <iostream> using namespace std; int g(float A[] , int L , int H) { if (L==H) if (A[L] > 0.0) return 1; else return 0; int M = (L+H)/2; return g(A,L,M)+ g(A,M+1,H); } int main (void) { float A[] = {-1.5 ,3.1,-5.2,0.0}; g(A,0,3); system ("pause"); return 0; } its asking me what is return by the function g and what the function does here is what i got so far first call is g(A , 0 ,3) -total skip the IF statement and M = 1 since it its a int -return g(A,1,3) + g(A,2 3) second call - g(A

问题 I have a record : type node = { content : string; parent : node option; branch : string option; children : seq<node> option; } Which I want to instantiate this way : let rec treeHead = { content = "Value" parent = None; branch = None; children = tree (Some(treeHead)) rows; }; Where let rec tree (parent:node option) (rows:seq<CsvRow>) :seq<node> option Is a a recursive function that gets the children of a node (to construct a tree). So as you can see the object treeHead needs to call itself

问题 The problem consists in choosing the best option at every moment of the game following these rules: You can only pick the leftmost or the rightmost card. Your opponent will ALWAYS pick first, and will ALWAYS choose the highest card from either the leftmost or the rightmost card. If it's a tie, it will pick the rightmost. Take into consideration this is not always the best choice. Sometimes it's impossible to win, but you must anyway display the highest amout you can add by playing against

问题 I'm looking for something kind of like Object.keys but that works for potentially nested objects. It also shouldn't include keys that have object/array values (it should only include keys with immediate string/number/boolean values). Example A Input { "check_id":12345, "check_name":"Name of HTTP check", "check_type":"HTTP" } Expected output [ "check_id", "check_name", "check_type" ] Object.keys would work for flat cases like this, but not for nested cases: Example B Input { "check_id":12345,

问题 I want to display a tree of categories managed with the gem ancestry. I would like to use a helper which will recursively go through the tree and return the categories one by one, for the moment without html tags or content. module CategoriesHelper def display_tree(category) if category.has_children? category.children.each do |sub_category| display_tree(sub_category) puts(sub_category.name) # to check if it goes here end end category.name end end The category argument is one of the root

问题 How to get current recursion level in a PHP function ? I mean, is there any "magical" (or eventually normal) function like this : function doSomething($things) { if (is_array($things)) { foreach ($things as $thing) { doSomething($thing); } } else { // This is what I want : echo current_recursion_level(); } } I know I can use another function argument ( $level in this example) : function doSomething($things, $level = 0) { if (is_array($things)) { foreach ($things as $thing) { $level++;

问题 Without using recursion how can a stack overflow exception be thrown? 回答1: If you call enough methods, a stack overflow can occur anytime. Although, if you get stack overflow errors without using recursion, you may want to rethink how you're doing things. It's just so easy with recursion because in an infinite loop, you call a ton of methods. 回答2: Since no one else has mentioned it: throw new System.StackOverflowException(); You might do this when testing or doing fault-injection. 回答3: