LeetCode: NQueens

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

class Solution {
public:
    void dfs(vector<bool> &visit, vector<int> &rec, vector<vector<string>> &ret, int dep, int n) {
        if (dep == n) {
            vector<string> tmp(n, "");
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < n; j++) {
                    if (j == rec[i]) tmp[i] += 'Q';
                    else tmp[i] += '.';
                }
            }
            ret.push_back(tmp);
        }
        vector<bool> cur(n, false);
        for (int i = 0; i < dep; i++) {
            if (rec[i] + dep - i < n && rec[i] + dep - i >= 0) cur[rec[i]+dep-i] = true;
            if (rec[i] - dep + i < n && rec[i] - dep + i >= 0) cur[rec[i]-dep+i] = true;
        }
        for (int i = 0; i < n; i++) {
            if (!cur[i] && !visit[i]) {
                visit[i] = true;
                rec[dep] = i;
                dfs(visit, rec, ret, dep+1, n);
                rec[dep] = n;
                visit[i] = false;
            }
        }
    }
    vector<vector<string> > solveNQueens(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<vector<string>> ret;
        vector<bool> visit(n, false);
        vector<int> rec(n, n);
        dfs(visit, rec, ret, 0, n);
        return ret;
    }
};

 C#

public class Solution {
    public void dfs(ref List<bool> visit, ref List<int> rec, ref List<string[]> ans, int dep, int n) 
    {
        if (dep == n) {
            string[] tmp = new string[n];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < n; j++) {
                    if (j == rec[i]) tmp[i] += 'Q';
                    else tmp[i] += '.';
                }
            }
            ans.Add(tmp);
            return;
        }
        List<bool> cur = new List<bool>(n);
        for (int i = 0; i < n; i++) cur.Add(false);
        for (int i = 0; i < dep; i++) {
            if (rec[i] + dep - i < n && rec[i] + dep - i >= 0) cur[rec[i] + dep - i] = true;
            if (rec[i] - dep + i < n && rec[i] - dep + i >= 0) cur[rec[i] - dep + i] = true;
        }
        for (int i = 0; i < n; i++) {
            if (cur[i] == false && visit[i] == false) {
                visit[i] = true;
                rec[dep] = i;
                dfs(ref visit, ref rec, ref ans, dep+1, n);
                rec[dep] = n;
                visit[i] = false;
            }
        }
    }
    public List<string[]> SolveNQueens(int n) {
        List<string[]> ans = new List<string[]>();
        List<bool> visit = new List<bool>();
        List<int> rec = new List<int>();
        for (int i = 0; i < n; i++) {
            visit.Add(false);
            rec.Add(n);
        }
        dfs(ref visit, ref rec, ref ans, 0, n);
        return ans;
    }
}