LeetCode: N-Queens

很惊奇这题一次过了，不过我的code感觉比较冗长，建议看网上答案

 1 class Solution {
 2 public:
 3     void dfs(vector<bool> &visit, vector<int> &rec, vector<vector<string>> &ret, int dep, int n) {
 4         if (dep == n) {
 5             vector<string> tmp(n, "");
 6             for (int i = 0; i < n; i++) {
 7                 for (int j = 0; j < n; j++) {
 8                     if (j == rec[i]) tmp[i] += 'Q';
 9                     else tmp[i] += '.';
10                 }
11             }
12             ret.push_back(tmp);
13         }
14         vector<bool> cur(n, false);
15         for (int i = 0; i < dep; i++) {
16             if (rec[i] + dep - i < n && rec[i] + dep - i >= 0) cur[rec[i]+dep-i] = true;
17             if (rec[i] - dep + i < n && rec[i] - dep + i >= 0) cur[rec[i]-dep+i] = true;
18         }
19         for (int i = 0; i < n; i++) {
20             if (!cur[i] && !visit[i]) {
21                 visit[i] = true;
22                 rec[dep] = i;
23                 dfs(visit, rec, ret, dep+1, n);
24                 rec[dep] = n;
25                 visit[i] = false;
26             }
27         }
28     }
29     vector<vector<string> > solveNQueens(int n) {
30         // Start typing your C/C++ solution below
31         // DO NOT write int main() function
32         vector<vector<string>> ret;
33         vector<bool> visit(n, false);
34         vector<int> rec(n, n);
35         dfs(visit, rec, ret, 0, n);
36         return ret;
37     }
38 };

 1 public class Solution {
 2     public void dfs(ref List<bool> visit, ref List<int> rec, ref List<string[]> ans, int dep, int n) 
 3     {
 4         if (dep == n) {
 5             string[] tmp = new string[n];
 6             for (int i = 0; i < n; i++) {
 7                 for (int j = 0; j < n; j++) {
 8                     if (j == rec[i]) tmp[i] += 'Q';
 9                     else tmp[i] += '.';
10                 }
11             }
12             ans.Add(tmp);
13             return;
14         }
15         List<bool> cur = new List<bool>(n);
16         for (int i = 0; i < n; i++) cur.Add(false);
17         for (int i = 0; i < dep; i++) {
18             if (rec[i] + dep - i < n && rec[i] + dep - i >= 0) cur[rec[i] + dep - i] = true;
19             if (rec[i] - dep + i < n && rec[i] - dep + i >= 0) cur[rec[i] - dep + i] = true;
20         }
21         for (int i = 0; i < n; i++) {
22             if (cur[i] == false && visit[i] == false) {
23                 visit[i] = true;
24                 rec[dep] = i;
25                 dfs(ref visit, ref rec, ref ans, dep+1, n);
26                 rec[dep] = n;
27                 visit[i] = false;
28             }
29         }
30     }
31     public List<string[]> SolveNQueens(int n) {
32         List<string[]> ans = new List<string[]>();
33         List<bool> visit = new List<bool>();
34         List<int> rec = new List<int>();
35         for (int i = 0; i < n; i++) {
36             visit.Add(false);
37             rec.Add(n);
38         }
39         dfs(ref visit, ref rec, ref ans, 0, n);
40         return ans;
41     }
42 }

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posted @ 2013-04-10 09:17 ying_vincent 阅读(188) 评论(0) 收藏举报

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