java 解决世界最难数独

使用java算法解决世界最难数独，我这花费的时间是60ms，虽然我发现有些人可以做到40ms以内，可能是用c++写的，我这使用java给后来者一个借鉴吧，本人也不是写的很好，望各位批评指正。

总体思路就是先填一个数，然后再填一个数，每次都判断是否和数独规定冲突，冲突就回滚，然后继续算……

下面贴代码（一共两个类，不过多解释了）

package com.cy.sudoku;public class Main {public static void main(String[] args) {// TODO Auto-generated method stubint[][] sudokuform = new int[][]{{8,0,0,0,0,0,0,0,0},{0,0,3,6,0,0,0,0,0},{0,7,0,0,9,0,2,0,0},{0,5,0,0,0,7,0,0,0},{0,0,0,0,4,5,7,0,0},{0,0,0,1,0,0,0,3,0},{0,0,1,0,0,0,0,6,8},{0,0,8,5,0,0,0,1,0},{0,9,0,0,0,0,4,0,0}};long startTime = System.currentTimeMillis();new SudoKuUtils(sudokuform).sudoKu();System.out.println( "总耗时：" + (System.currentTimeMillis() - startTime)  + "ms");}}

package com.cy.sudoku;import java.util.ArrayList;import java.util.List;public class SudoKuUtils {// 待解决的数独表private int[][] sudokuform;// 我需要填写的答案的下标private List answerI, answerJ;private int[][] answer;// 我需要填写的答案数private int answerNum;public SudoKuUtils(int[][] sudokuform) {answerI = new ArrayList<>();answerJ = new ArrayList<>();this.sudokuform = sudokuform;getAnswerIndex();answerNum = answerI.size();}/** * 获得需要填写答案的位置的下标,存入两个list */public void getAnswerIndex() {answerI.clear();answerJ.clear();int[] answerIndex = new int[3];for (int i = 0; i < 9; i++) {for (int j = 0; j < 9; j++) {if (sudokuform[i][j] == 0) {answerI.add(i);answerJ.add(j);}}}}/** * 主要入口 */public void sudoKu() {for (int i = 0; i < answerI.size(); i++) {for (int a = 1; a < 10; a++) {if (isOk((int) answerI.get(i), (int) answerJ.get(i), a)&& a > sudokuform[(int) answerI.get(i)][(int) answerJ.get(i)]) {sudokuform[(int) answerI.get(i)][(int) answerJ.get(i)] = a;// System.out.println((int) answerI.get(i) + " " + (int)// answerJ.get(i) + " " + a);break;} else if (a == 9) {if (i == 0) {System.out.println("无解");return;}sudokuform[(int) answerI.get(i)][(int) answerJ.get(i)] = 0;if (i < 1) {i = i - 1;} else {i = i - 2;}break;}}}print(sudokuform);}/** * 传入i( 行)j(列)以及填入的值,判断是否符合要求 */public boolean isOk(int i, int j, int answer) {for (int n = 0; n < 9; n++) {if (sudokuform[i][n] == answer) {return false;}}for (int n = 0; n < 9; n++) {if (sudokuform[n][j] == answer) {return false;}}if (i <= 2) {if (j <= 2) {for (int n = 0; n < 3; n++) {for (int m = 0; m < 3; m++) {if (sudokuform[n][m] == answer) {return false;}}}} else if (j <= 5) {for (int n = 0; n < 3; n++) {for (int m = 3; m < 6; m++) {if (sudokuform[n][m] == answer) {return false;}}}} else {for (int n = 0; n < 3; n++) {for (int m = 6; m < 9; m++) {if (sudokuform[n][m] == answer) {return false;}}}}} else if (i <= 5) {if (j <= 2) {for (int n = 3; n < 6; n++) {for (int m = 0; m < 3; m++) {if (sudokuform[n][m] == answer) {return false;}}}} else if (j <= 5) {for (int n = 3; n < 6; n++) {for (int m = 3; m < 6; m++) {if (sudokuform[n][m] == answer) {return false;}}}} else {for (int n = 3; n < 6; n++) {for (int m = 6; m < 9; m++) {if (sudokuform[n][m] == answer) {return false;}}}}} else {if (j <= 2) {for (int n = 6; n < 9; n++) {for (int m = 0; m < 3; m++) {if (sudokuform[n][m] == answer) {return false;}}}} else if (j <= 5) {for (int n = 6; n < 9; n++) {for (int m = 3; m < 6; m++) {if (sudokuform[n][m] == answer) {return false;}}}} else {for (int n = 6; n < 9; n++) {for (int m = 6; m < 9; m++) {if (sudokuform[n][m] == answer) {return false;}}}}}return true;}/** * 输出二维数组 *  * @param a */public void print(int[][] a) {for (int i = 0; i < 9; i++) {for (int j = 0; j < 9; j++) {System.out.print(" " + a[i][j] + " ");if (j == 8) {System.out.println();}}}}/** * 输出一维数组 *  * @param a */public void print(int[] a) {for (int i = 0; i < 9; i++) {System.out.print(" " + a[i] + " ");}}}