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| class Solution {
boolean[][] visited;
private List<List<String>> res = new ArrayList<List<String>>();
public List<List<String>> solveNQueens(int n) {
List<StringBuffer> list = new ArrayList<StringBuffer>();
visited = new boolean[3][n*2];
for(int i=0; i<n;i++) {
StringBuffer sbuf = new StringBuffer();
for(int j=0;j<n;j++){
sbuf.append('.');
}
list.add(sbuf);
}
search(list, 0, n);
return res;
}
public void search(List<StringBuffer> list, int cur, int n) {
if(cur==n) {
ArrayList<String> list2 = new ArrayList<>();
for(StringBuffer sb: list) {
list2.add(sb.toString());
}
res.add(list2);
return ;
}else {
for(int i=0;i<n;i++) {
if(!visited[0][i]&&!visited[1][cur+i]
&&!visited[2][cur-i+n]) {
list.get(cur).setCharAt(i, 'Q');
visited[0][i] = visited[1][cur+i] = visited[2][cur-i+n]=true;
search(list, cur+1, n);
list.get(cur).setCharAt(i, '.');
visited[0][i] = visited[1][cur+i] = visited[2][cur-i+n] = false;
}
}
}
}
}
|
