两年前我用C语言穷举法完成了，给老师检查，老师无情嘲笑了我的代码，今天做LeetCode又碰到了它。
虽然这次写得很烂，还是记录一下。
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| import java.util.ArrayList;
import java.util.List;
public class Queen {
public static void main(String[] args) {
int n = 5;
List<List<String>> answer = solveNQueens(n);
System.out.println(answer);
}
public static List<List<String>> solveNQueens(int n) {
List<List<String>> bord = initBord(n);
List<List<String>> answer = new ArrayList<>();
start(n,bord,answer,0);
return answer;
}
public static void start(int n, List<List<String>> bord,List<List<String>> answer, int row){
if (row == n) {
List<String> temp = new ArrayList<>();
for(int i = 0; i < n; i ++){
List<String> nowRow = bord.get(i);
StringBuilder answerRow = new StringBuilder();
for(int j = 0; j < n; j ++){
if(nowRow.get(j).equals("Q")){
answerRow.append("Q");
}else{
answerRow.append(".");
}
}
temp.add(String.valueOf(answerRow));
}
answer.add(temp);
return;
}
List<String> nowRow = bord.get(row);
for (int col = 0;col < n; ++col) {
if (check (row, col, bord, n)) {
setOne(row,col,"Q",bord);
start(n, bord, answer,row+1);
setOne(row,col,"0",bord);
}
}
}
public static List<List<String>> initBord(int n){
List<List<String>> bord = new ArrayList<>();
for(int i = 0; i < n; i++){
List<String> temp = new ArrayList<>();
for(int j = 0; j < n; j++){
temp.add("0");
}
bord.add(temp);
}
return bord;
}
public static void setOne(int x,int y, String s, List<List<String>> bord){
List<String> row = bord.get(x);
row.set(y,s);
bord.set(x,row);
}
public static boolean check(int x,int y, List<List<String>> bord,int n){
List<String> row = bord.get(x);
for(int i = 0; i < n; i++){
if(row.get(i).equals("Q")) {
return false;
}
}
for(int i = 0; i < n; i ++){
List<String> row1 = bord.get(i);
if(row1.get(y).equals("Q")){
return false;
}
}
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
List<String> row2 = bord.get(i);
if((Math.abs(i-x) == Math.abs(j-y))&&(row2.get(j).equals("Q"))){
return false;
}
}
}
return true;
}
}
|
