# Questions tagged [algorithm]

A puzzle related to algorithmics (a main concept in computer science).

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### Find the result of this dual key cipher

I came up with a neat little cipher that I'm calling the dual key cipher. The basic premise is that there are two cipher keys that, when used together can decode the cipher text against a given ...
155 views

421 views

### Place 16 queens in a $16\times 16$ board peacefully, also in subboards!

What is the smallest number, $n$ in which $n$ queens can live in a $n\times n$ board peacefully? Of course not more than 8. ☺ (read about the eight queen puzzle) But this was not the question. ...
510 views

### Calculating column number based on Excel alpha column reference [closed]

Here's a super fun brain teaser!!! Can you give me a mathematical equation to calculate the column number of a Microsoft Excel column, given the alphabetic column reference? Let X, Y, & Z ...
6k views

### Check sudoku solvability

With a blank grid, I put and number (1-9) any cell, the Sudoku has n solutions. I continue filling any blank cells with numbers that satisfy the constraints, so the Sudoku still has many solutions, ...
2k views

### Sorting 4 numbers using “maximum” & “minimum” between 2 numbers

I'm having some trouble solving this thing. You're given an unlimited number of "black boxes" which will return the maximum or the minimum between 2 inputs. The goal is to compare/sort 4 numbers ...
2k views

### 3x3x3 Rubik's Cube Illegal State

After I learned how to solve a 3x3 Rubik's Cube and a 4x4 Rubik's Revenge, I began challenging myself to solve the cubes to different states rather than the normal solid sides. For instance, I'd solve ...
101 views

### Last number in barcode [closed]

Find solution, how work algoritem for last, control number in 8 places barcode. Here is some results: Here we got last number 8 Here we got last number 7: Here we got last number 5 What is last ...
508 views

### Half-reverse operation on binary strings

Is there an algorithm that you can apply twice to an input string of $0$s and $1$s in order to reverse it? In other words, is there a function $f : \mathrm B \to \mathrm B$ on the set of binary ...
Imagine a game on a grid of $m$ rows and $n$ columns. Player One will place a fixed number $r$ of markers in each row. Player Two will select the two rows which maximize the number of columns having ...