backtracking

Number of tours through m x n grid?

由 谁说我不能喝 提交于 2019-12-08 09:07:12
问题 Let T(x,y) be the number of tours over a X × Y grid such that: the tour starts in the top left square the tour consists of moves that are up, down, left, or right one square, the tour visits each square exactly once, and the tour ends in the bottom left square. It’s easy to see, for example, that T(2,2) = 1, T(3,3) = 2, T(4,3) = 0, and T(3,4) = 4. Write a program to calculate T(10,4). I have been working on this for hours ... I need a program that takes the dimensions of the grid as input and

Application of Backtracking algorithm to find minimum number of semester to graduate

由 南笙酒味 提交于 2019-12-08 03:11:55
问题 I'm taking input from a file , which contains No of courses and max allowed course per semester All Course name(5 alphanumeric max) couse name,Offered sem, number of prereqs, Prereq courses. -1 and -1 at the end The output will be the minimum number of semester to complete all courses. This is my code, so that you know I've done work. My code is compiling and executing, but not showing the number of sems to complete courses. Please tell me where I'm doing wrong #include<stdio.h> #include

Sellers and Buyers

由 試著忘記壹切 提交于 2019-12-07 22:29:06
问题 This is a followup of this question. Lets say there are several sellers and buyers, each seller has an amount of products in stock, each buyer also has a number of products they want to get. Now you are asked to find a best strategy to satisfy as many buyers as possible. (Here satisfy does not mean giving each buyer as many products as possible, if the amount of products available to this buyer is smaller than his requirement, this transaction can not be done and this buyer is not satisfied.

Algorithm of N queens

由 白昼怎懂夜的黑 提交于 2019-12-07 11:15:50
问题 Algorithm NQueens ( k, n) //Prints all Solution to the n-queens problem { for i := 1 to n do { if Place (k, i) then { x[k] := i; if ( k = n) then write ( x [1 : n] else NQueens ( k+1, n); } } } Algorithm Place (k, i) { for j := 1 to k-1 do if (( x[ j ] = // in the same column or (Abs( x [ j ] - i) =Abs ( j – k ))) // or in the same diagonal then return false; return true; } The above code is for solving N Queens problem using backtracking.I think that it can place the first 2 queens of two

How to Solve N-Queens in Scheme?

由 倾然丶 夕夏残阳落幕 提交于 2019-12-07 10:36:35
问题 I'm stuck on the extended exercise 28.2 of How to Design Programs. I used a vector of true or false values to represent the board instead of using a list. This is what I've got which doesn't work: #lang Scheme (define-struct posn (i j)) ;takes in a position in i, j form and a board and ; returns a natural number that represents the position in index form ;example for board xxx ; xxx ; xxx ;(0, 1) -> 1 ;(2, 1) -> 7 (define (board-ref a-posn a-board) (+ (* (sqrt (vector-length a-board)) (posn-i

Implementing a backtrack search with heuristic?

由 本秂侑毒 提交于 2019-12-07 01:22:49
问题 I'm getting quite interested in search algorithms and backtrack programming. For now, I have implemented Algorithm X (see my other post here: Determine conflict-free sets? ) to solve an exact cover problem. This works very well but I'm now interested in solving this with a more basic variant of backtracking. I just can't figure out how this can be done. The problem description is the same as before: Suppose you have a bunch of sets, whereas each set has a couple of subsets. Set1 = { (banana,

Can we solve N Queens without backtracking? and How to calculate and what will be the complexity of the backtracking solution?

由 巧了我就是萌 提交于 2019-12-06 12:35:35
问题 I have tried solving this problem with backtracking and it prints all possible solutions. Two questions came up: 1. Can i implement n queen using other techniques? 2. Is it possible to make the code below print only the first solution and then terminate? My current code uses backtracking: n = 8 x = [-1 for x in range(n)] def safe(k,i): for j in xrange(k): if x[j] == i or abs(x[j] - i) == abs(k - j) : return False return True def nqueen(k): for i in xrange(n): if safe(k,i): x[k] = i if k == n

Crypt Kicker Algorithm and Solution, what went wrong?

由 有些话、适合烂在心里 提交于 2019-12-06 12:29:55
问题 Problem Description: Crypt kicker algorithm is a well-known encryption algorithm but less secure. This UVa problem is to decrypt lines based on this method. The problem statement is as follows: 843 Crypt Kicker A common but insecure method of encrypting text is to permute the letters of the alphabet. That is, in the text, each letter of the alphabet is consistently replaced by some other letter. So as to ensure that the encryption is reversible, no two letters are replaced by the same letter.

Is backtracking absolutely necessary for cycle detection using DFS in directed graph?

由 [亡魂溺海] 提交于 2019-12-06 11:26:22
I came across this SO post where it is suggested that cycle detection using DFS in a directed graph is faster because of backtracking. Here I quote from that link: Depth first search is more memory efficient than breadth first search as you can backtrack sooner. It is also easier to implement if you use the call stack but this relies on the longest path not overflowing the stack. Also if your graph is directed then you have to not just remember if you have visited a node or not, but also how you got there. Otherwise you might think you have found a cycle but in reality all you have is two

Tracking an App's running time iOS

由 瘦欲@ 提交于 2019-12-06 03:51:31
问题 Is there a way that I can know how long the apps in the foreground has been running? I have three possible solutions in mind: I. use battery consumption and battery consumption rate (iOS 8 and later tell you the battery usage of the app, but the batter consumption will be difficult to handle) II. use system processes monitor III. use Apple's diagnostics logs. This approach is quite "backdoor." Plus I am not sure if Apple allows us to use the information or not. Can someone tell me if any of
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