Randomly generate a Sudoku

Recently learned to write GUI program with Java, feel from doing a small thing to start the best, choose to write some small games to begin, the first is a single game.

Http://en.wikipedia.org/wiki/Sudoku

The first step in writing a Sudoku game is how to generate a primitive Sudoku problem, the simplest way to generate Sudoku is to randomly generate a complete Sudoku and then remove some numbers from it so that you can generate a Sudoku problem. So there is a need to consider how to randomly generate a complete Sudoku, which is considered to be generated using backtracking methods:

• Insert a 1~9 value at a location in the Sudoku
• If the value is inserted normally, the recursion is inserted at the next position
• If no value can be inserted in this position, the value inserted at the previous position is traced back
• Recursive the above steps until all positions are inserted with the appropriate values

ImportJava.util.Random; Public classMain {Private Static int[] num =New int[81]; Private StaticRandom random =NewRandom (); /*** Randomly generate a Sudoku *@returnreturns a randomly generated Sudoku*/     Public Static int[] Generate () { for(inti = 0; I < 81; i++) {Num[i]= 0; } Solve (0); returnnum; }    /*** Recursive generation of the value of the Sudoku position I *@paramSudoku Position I *@returnwhether position I can fill in values*/    Private Static BooleanSolveinti) {/*returns True if the 81 lattices have been filled*/        if(i = = 81) {            return true; }        /*If position I has already filled in the appropriate value, the value of the next position is generated recursively*/        Else if(num[i]! = 0) {            returnSolve (i + 1)); }        /*If you exactly need to fill in the value of position I*/        Else {            /*storing the values that each location might produce with an array randorder, which is 1~9*/            int[] Randorder =New int[10];  for(intval = 1; Val < 10; val++) {Randorder[val]=Val; }            /*changes the array randorder to a randomly stored 1~9 array*/             for(intval = 1; Val < 10; val++) {                intRand = Random.nextint (10); intTMP =Randorder[rand]; Randorder[rand]=Randorder[val]; Randorder[val]=tmp; }            /*in position I randomly fills in a value and determines whether it is valid*/             for(intval = 1; Val < 10; val++) {                /*if a random number in the 1~9 that is filled in position i is valid*/                if(Islegal (i, Randorder[val])) {/*The random value is put in position I*/Num[i]=Randorder[val]; /*explore whether the next position of I can be filled in correctly, and return true if possible*/                    if(Solve (i + 1)) {                        return true; }                }            }        }        /*If you cannot fill any of the values in the 1~9 at position I, you need to backtrack*/Num[i]= 0; return false; }    /*** In position I fill in the value number is valid, by the column and the Small matrix judgment *@paramfill in position I *@paramfill in the number of position I value *@returnin position I fill in the number value is valid*/    Private Static BooleanIslegal (intIintvalue) {        /*determine if the row is valid*/        if(!Isrowlegal (i, value)) {            return false; }        /*determine if the column is valid*/        if(!Iscollegal (i, value)) {            return false; }        /*determine if the small matrix is valid*/        if(!Issublegal (i, value)) {            return false; }        return true; }    /*** Determine if the value line rule in position I fills in is satisfied *@paramfill in position I *@paramfill in the number of position I value *@returnin position I fills in the number value row rule is valid*/    Private Static BooleanIsrowlegal (intIintvalue) {        introw = I/9;  for(intval = 0; Val < 9; val++) {            if(Value = = Num[row * 9 +Val]) {                return false; }        }        return true; }    /*** Determine if the Value column rule in position I fills in is satisfied *@paramfill in position I *@paramfill in the number of position I value *@returnin position I fills in the number Value column rule is valid*/    Private Static BooleanIscollegal (intIintvalue) {        intCol = i% 9;  for(intval = 0; Val < 9; val++) {            if(Value = = Num[val * 9 +Col]) {                return false; }        }        return true; }    /*** Determine if the value in position I fills in the small matrix rule is satisfied *@paramfill in position I *@paramfill in the number of position I value *@returnin position I fills in the number value small matrix rule is valid*/    Private Static BooleanIssublegal (intIintvalue) {        introw = I/9; intCol = i% 9; intXOFF = ROW/3 * 3; intYoff = COL/3 * 3;  for(intx = 0; x < 3; X + +) {             for(inty = 0; Y < 3; y++) {                if(Value = = num[(xOff + x) * 9 + Yoff +y]) {return false; }            }        }        return true; }     Public Static voidMain (string[] args) {int[] Grid =New int[9] [9]; int[] Sudoku =New int[81];  for(inti = 0; I < 81; i++) {Sudoku[i]= 0; } Sudoku=generate ();  for(inti = 0; I < 9; i++) {             for(intj = 0; J < 9; J + +) {Grid[i][j]= Sudoku[i * 9 +J]; }} System.out.println ("***********************");  for(inti = 0; I < 9; i++) {             for(intj = 0; J < 9; J + +) {System.out.print (Grid[i][j]+ " "); if(j% 3 = = 2) {System.out.print ("| ");            }} System.out.println (); if(i% 3 = = 2) {System.out.println ("***********************"); }        }    }}

Operation Result:

2 3 9 | 7 6 8 | 1 5 4 | 8 4 7 | 1 5 3 | 6 9 2 | 1 5 6 | 2 4 9 | 8 7 3 | 3 7 8 | 5 2 1 | 9 4 6 | 6 1 5 | 4 9 7 | 3 2 8 | 9 2 4 | 3 8 6 | 5 1 7 | 5 8 1 | 6 7 2 | 4 3 9 | 4 9 2 | 8 3 5 | 7 6 1 | 7 6 3 | 9 1 4 | 2 8 5 | 2 4 6 | 7 5 3 | 9 8 1 | 9 1 8 | 6 4 2 | 5 7 3 | 5 7 3 | 9 8 1 | 6 4 2 | 4 5 7 | 3 2 9 | 8 1 6 | 8 3 9 | 5 1 6 | 7 2 4 | 6 2 1 | 8 7 4 | 3 5 9 | 3 8 2 | 1 9 7 | 4 6 5 | 7 6 4 | 2 3 5 | 1 9 8 | 1 9 5 | 4 6 8 | 2 3 7 | ***********************

Randomly generate a Sudoku