backtracking

问题 This weekend I worked on a Sudoku Solver (Ruby quiz) based on a backtracking algorithm. The sudoku is loaded in an array sudoku_arr of 81 integers (9x9 grid) where 0's are empty spots. There is a valid? method which checks if the sudoku_arr can be a valid sudoku. The official backtracking algorithm goes like this: try value on next empty spot, check if it is valid sudoku, if not increase value by 1 (upto 9), if valid go on and try first value on next spot, if not increase value of previous 0.

问题 The problem is next. I created an input field which has validation and this is valid data: 1-12, 14, 16, 22, 25-35, 41, 49, 55-90 1230-1992, 2001-2099, 9931 1-2 13 1,3,4,5,6,10 all Basically, any combination of those numbers (ranges, comma-separated ranges, comma-separated number, spaces after commas, no spaces after commas, word: 'all') My RegEx: /^(([0-9]{0,4},?\s{0,})+([0-9]{1,4}-[0-9]{1,4}){0,},?\s{0,})+$|^(all)$|^([0-9]{1,4}-[0-9]{1,4}){0,},?\s{0,}$/ It works almost fine, there is only 1

问题 I have a problem that is seemingly solvable by enumerating all possible solutions and then finding the best. In order to do so, I devised a backtracking algorithm that enumerates and stores the best solution if found. It works fine so far. Now, I wanted to port this algorithm to CUDA. Therefore, I created a procedure that generates some distinct basic cases. These basic cases should be processed in parallel on the GPU. If one of the CUDA-threads finds an optimal solution, all the other

问题 I have a triangle with two-hundred rows, where I have to find the maximum distance to get from the top to the bottom of the triangle. 5 9 8 5 4 6 9 7 3 4 Here, the shortest distance would be 5+8+4+3=20. The maximum distance would be 5+9+5+9=28. I have a good idea of the algorithm I want to implement but I am struggling to turn it into code. My plan is: start at the 2nd to last row, add the maximum of the possible paths from the bottom row, and iterate to the top. For instance, the above

问题 So I've been trying to solve this assignment whole day, just can't get it. The following function accepts 2 strings, the 2nd (not 1st) possibly containing * 's (asterisks). An * is a replacement for a string (empty, 1 char or more), it can appear appear (only in s2) once, twice, more or not at all, it cannot be adjacent to another * ( ab**c ), no need to check that. public static boolean samePattern(String s1, String s2) It returns true if strings are of the same pattern. It must be recursive

问题 How to calculate time complexity for these backtracking algorithms and do they have same time complexity? If different how? Kindly explain in detail and thanks for the help. 1. Hamiltonian cycle: bool hamCycleUtil(bool graph[V][V], int path[], int pos) { /* base case: If all vertices are included in Hamiltonian Cycle */ if (pos == V) { // And if there is an edge from the last included vertex to the // first vertex if ( graph[ path[pos-1] ][ path[0] ] == 1 ) return true; else return false; } /

问题 I'm struggling with a backtracking algorithm to determine wether a Sudoku has a unique solution or if it has multiple Solutions. Here's the backtracking code i use: static boolean solve(int i, int j, int[][] cells) { if (i == 9) { i = 0; if (++j == 9) return true; } if (cells[i][j] != 0) // skip filled cells return solve(i+1,j,cells); for (int val = 1; val <= 9; ++val) { if (legal(i,j,val,cells)) { cells[i][j] = val; if (solve(i+1,j,cells)) return true; } } cells[i][j] = 0; // reset on

问题 I created a Sudoku Backtracking solver and it works just fine, but now i want to give out an error if the sudoku cant be solved because it isnt valid for example if this sudoku is given: http://img5.imageshack.us/img5/2241/sudokugq.jpg what can i do to make my solving method give out an error if it isnt solveable? I always end up with Zeros or stuck in a loop. public void solve( int row, int col ) throws Exception { // Throw an exception to stop the process if the puzzle is solved if( row > 8

问题 I´m facing a problem with constructing a randomised matrix where I partially already have values (that need to stay fixed - so no further randomisation there). Lets see: matrix should end up being 10 by 10 n <- 10 I do want my first rows to be the data I enter. e.g: row1<- c(1,4,7,6,5,3,2,8,9,10) row2<- c(10,7,3,2,1,4,5,9,8,6) row3<- c(9,2,4,3,8,7,10,1,6,5) To bild a matrix with 10 rows (and 10 columns) I combined those rows with samples (no replace because I want each number to be unique in

问题 The term fib(N,F) is true when F is the N th Fibonacci number. The following Prolog code is generally working for me: :-use_module(library(clpfd)). fib(0,0). fib(1,1). fib(N,F) :- N #> 1, N #=< F + 1, F #>= N - 1, F #> 0, N1 #= N - 1, N2 #= N - 2, F1 #=< F, F2 #=< F, F #= F1 + F2, fib(N1,F1), fib(N2,F2). When executing this query (in SICStus Prolog), the first (and correct) match is found for N (rather instantly): | ?- fib(X,377). X = 14 ? When proceeding (by entering ";") to see if there are