-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathNQueens.java
46 lines (43 loc) · 1.25 KB
/
NQueens.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
/**
* Created by Yuzhang on 1/30/17.
*/
import java.util.*;
public class NQueens {
public List<List<Integer>> nqueens(int n) {
List<List<Integer>> result = new ArrayList<>();
if (n <= 0) {
return result;
}
List<Integer> cur = new ArrayList<>();
helper(result, cur, n);
return result;
}
private void helper(List<List<Integer>> result, List<Integer> cur, int n) {
if (cur.size() == n) {
result.add(new ArrayList<>(cur));
return;
}
for (int i = 0; i < n; i++) {
if (valid(cur, i)) {
cur.add(i);
helper(result, cur, n);
cur.remove(cur.size() - 1);
}
}
}
private boolean valid(List<Integer> cur, int col) {
int row = cur.size();
for (int i = 0; i < row; i++) {
if (cur.get(i) == col || Math.abs(cur.get(i) - col) == Math.abs(row - i)) {
return false;
}
}
return true;
}
public static void main(String args[]) {
NQueens solution = new NQueens();
List<List<Integer>> result = new ArrayList<>();
result = solution.nqueens(4);
System.out.println(result);
}
}