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Solution.java
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Solution.java
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public class Solution {
public int totalNQueens(int n) {
return solveNQueens(n).size();
}
public List<List<String>> solveNQueens(int n) {
//装n皇后的数组
int[] nums=new int[n];
//答案
List<List<String>> ans=new ArrayList<List<String>>();
int i=0;
while (true) {
//所有可能已经尝试完毕,退出游戏
if (i<0) {
return ans;
}
//成功尝试出一种答案, 装载答案
if (i==n) {
List<String> list=new ArrayList<String>();
for (int j = 0; j < nums.length; j++) {
StringBuffer sb=new StringBuffer();
for (int k = 0; k < n; k++) {
if (k!=nums[j]) {
sb.append(".");
}else {
sb.append("Q");
}
}
list.add(sb.toString());
}
ans.add(list);
//回退
i--;
while (nums[i]==n) {
nums[i]=0;
i--;
}
nums[i]++;
}else {
if (nums[i]==n) {
//回退
while (i>=0&&nums[i]==n) {
nums[i]=0;
i--;
}
if (i>=0) {
nums[i]++;
}
}else {
if (f(nums,i,nums[i])) {
i++;
}else {
nums[i]++;
}
}
}
}
// return ans;
}
public boolean f(int[] nums,int x,int val){
for (int i = 0; i < x; i++) {
int t=x-i;
if (val==nums[i]||val==nums[i]+t||val==nums[i]-t) {
return false;
}
}
return true;
}
}