puzzle

I'm trying to find an algorithm which "breaks the safe" by typing the keys 0-9. The code is 4 digits long. The safe will be open where it identifies the code as substring of the typing. meaning, if the code is "3456" so the next typing will open the safe: "123456". (It just means that the safe is not restarting every 4 keys input). Is there an algorithm which every time it add one digit to the sequence, it creates new 4 digits number (new combinations of the last 4 digits of the sequence\string)? thanks, km. Editing (I post it years ago): The question is how to make sure that every time I set

I'm interested making an implementation of the 14-15 puzzle : I'm creating an array with the values 0 - 15 in increasing order: S = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 } Now, what I want to do is shuffle them to create a new instance of the puzzle. However, I know that if I create a board with an "odd permutation" than it is unsolvable. Wikipedia says I need to create the puzzle with an even permutation. I believe this means that I simply have to do ensure I do an even number of swaps? How would I modify Fisher-Yates so I ensure I end up with an even permutation at the end?

I have a class, which I have simplified to this: final class Thing { private final int value; public Thing(int value) { this.value = value; } public int getValue() { return value; } @Override public String toString() { return Integer.toString(value); } } I want to sort an array of this thing. So I have created a simple copmarator: private static final Comparator<Thing> reverse = new Comparator<Thing>() { public int compare(Thing a, Thing b) { return a.getValue() - b.getValue(); } }; I then use the two argument form of Arrays.sort . This works fine for my test cases, but sometimes it goes all

Question: given an integer number n, print the numbers from 1 up to n 2 like this: n = 4 result is: 01 02 03 04 12 13 14 05 11 16 15 06 10 09 08 07 How do you solve it (apart from the solution provided in the link below)? http://www.programmersheaven.com/mb/CandCPP/81986/81986/problem-in-making-ap-c++-program/?S=B20000 I'm looking in another direction. So far, I'm trying to figure out if I could obtain the ordered list of positions I have to fill in. Here's what Im looking into: is there a way to obtain the "fdisp" so as to solve the problem that way, instead of "walk" in the matrix? matrix =

A buddy of mine had these puzzles and this is one that is eluding me. Here is the problem, you are given a number and you want to return that number times 3 and divided by 16 rounding towards 0. Should be easy. The catch? You can only use the ! ~ & ^ | + << >> operators and of them only a combination of 12. int mult(int x){ //some code here... return y; } My attempt at it has been: int hold = x + x + x; int hold1 = 8; hold1 = hold1 & hold; hold1 = hold1 >> 3; hold = hold >> 4; hold = hold + hold1; return hold; But that doesn't seem to be working. I think I have a problem of losing bits but I