recursion

问题 I need to implement a method that will scan a string of JSON for a particular targetField and either return the value of that field (if it exists), or null (if it doesn't): // Ex: extractFieldValue(/{ "fizz" : "buzz" }/, 'fizz') => 'buzz' // Ex: extractFieldValue(/{ "fizz" : "buzz" }/, 'foo') => null String extractFieldValue(String json, String targetField) { // ... } This solution has to be recursive and work at any nesting-level in the (hierarchical) JSON string. Also it needs to work for

问题 I learning more and more about Erlang language and have recently faced some problem. I read about foldl(Fun, Acc0, List) -> Acc1 function. I used learnyousomeerlang.com tutorial and there was an example (example is about Reverse Polish Notation Calculator in Erlang): %function that deletes all whitspaces and also execute rpn(L) when is_list(L) -> [Res] = lists:foldl(fun rpn/2, [], string:tokens(L," ")), Res. %function that converts string to integer or floating poitn value read(N) -> case

问题 I learning more and more about Erlang language and have recently faced some problem. I read about foldl(Fun, Acc0, List) -> Acc1 function. I used learnyousomeerlang.com tutorial and there was an example (example is about Reverse Polish Notation Calculator in Erlang): %function that deletes all whitspaces and also execute rpn(L) when is_list(L) -> [Res] = lists:foldl(fun rpn/2, [], string:tokens(L," ")), Res. %function that converts string to integer or floating poitn value read(N) -> case

问题 I'm looking to explore different algorithms, both recursive and dynamic programming, that checks if one arrayA is a subsequence of arrayB. For example, arrayA = [1, 2, 3] arrayB = [5, 6, 1, 7, 2, 9, 3] thus, arrayA is indeed a subsequence of arrayB. I've tried a few different searches, but all I can seem to find is algorithms to compute the longest increasing subsequence. 回答1: Since you must match all elements of arrayA to some elements of arrayB , you never need to backtrack . In other words

问题 I would like to split a list of words separated through integers into a list of lists. Sample query and expected result: ?- separatewords([h,e,l,l,o,1,o,v,e,r,3,t,h,e,r,e], X). X = [[h,e,l,l,o],[o,v,e,r],[t,h,e,r,e]]. The following things I already achieved: Splitting the list into one list before the first integer and one after the first integer: Sample query with result: ?- take1word([h,e,l,l,o,1,o,v,e,r,3,t,h,e,r,e], X, Y). X = [h,e,l,l,o], Y = [o,v,e,r,3,t,h,e,r,e]. % OK My code:

问题 Consider this code, which computes the maximum element of an array. #include <stdio.h> int maximum(int arr[], int n) { if (n == 1) { return arr[0]; } else { int max = maximum(arr, n-1); printf("Largest element : %d\n", max); return 5; // return arr[n-1] > max ? arr[n-1] : max; } } int main() { int array[5] = {5, 23, 28, 7, 1}; printf("Maximum element of the array is: %d", maximum(array, 5)); return 0; } Why is the else block called four (4) times? 回答1: The function is recursive, thus it will

问题 Consider this code, which computes the maximum element of an array. #include <stdio.h> int maximum(int arr[], int n) { if (n == 1) { return arr[0]; } else { int max = maximum(arr, n-1); printf("Largest element : %d\n", max); return 5; // return arr[n-1] > max ? arr[n-1] : max; } } int main() { int array[5] = {5, 23, 28, 7, 1}; printf("Maximum element of the array is: %d", maximum(array, 5)); return 0; } Why is the else block called four (4) times? 回答1: The function is recursive, thus it will

问题 Is there a way to use linq to get a list of textboxes in a web page regardless of their position in the tree hierarchy or containers. So instead of looping through the ControlCollection of each container to find the textboxes, do the same thing in linq, maybe in a single linq statement? 回答1: One technique I've seen is to create an extension method on ControlCollection that returns an IEnumerable ... something like this: public static IEnumerable<Control> FindAll(this ControlCollection

问题 I've been searching the web for an implementation of the Sieve of Eratosthenes in scheme and although I came up with a lot of content, none of them seemed to have made it like I need it to be done. The problem is most algorithms either use a static end or use iteration. This paired with my lack of knowledge of the language led me to ask all of you for help. I need an implementation of the Sieve that takes in one argument (number to Sieve until), uses only recursion and has a list of "cons" of

问题 With the question Listing all the contents of a directory by breadth-first order results in low efficiencyI learned that the low efficiency is due to a strange behavior of the recursive monad functions. Try sequence $ map return [1..]::[[Int]] sequence $ map return [1..]::Maybe [Int] and ghci will fall into an endless calculation. If we rewrite the sequence function in a more readable form like follows: sequence' [] = return [] sequence' (m:ms) = do {x<-m; xs<-sequence' ms; return (x:xs)} and