LeetCode: Permutations

一次过

class Solution {
public:
    void dfs(int dep, int maxdep, vector<int> &tmp, vector<vector<int>> &ret, vector<int> num, vector<bool> &visit) {
        if (dep == maxdep) {
            ret.push_back(tmp);
            return;
        }
        for (int i = 0; i < maxdep; i++) {
            if (!visit[i]) {
                visit[i] = true;
                tmp.push_back(num[i]);
                dfs(dep+1, maxdep, tmp, ret, num, visit);
                tmp.pop_back();
                visit[i] = false;
            }
        }
    }
    vector<vector<int> > permute(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        sort(num.begin(), num.end());
        int size = num.size();
        vector<int> tmp;
        vector<vector<int>> ret;
        vector<bool> visit(size, false);
        dfs(0, size, tmp, ret, num, visit);
        return ret;
    }
};

 推荐下一段代码

class Solution {
public:
    void dfs(vector<int> &num, vector<vector<int> > &ans, int k) {
        if (k == num.size()) {
            ans.push_back(num);
            return;
        }
        for (int i = k; i < num.size(); ++i) {
            swap(num[i], num[k]);
            dfs(num, ans, k+1);
            swap(num[i], num[k]);
        }
    }
    vector<vector<int> > permute(vector<int> &num) {
        vector<vector<int> > ans;
        if (num.size() == 0) return ans;
        sort(num.begin(), num.end());
        dfs(num, ans, 0);
        return ans;
    }
};

 C#

public class Solution {
    public List<List<int>> Permute(int[] nums) {
        List<List<int>> ans = new List<List<int>>();
        if (nums.Length == 0) return ans;
        Array.Sort(nums);
        dfs(nums, ref ans, 0);
        return ans;
    }
    public void dfs(int[] nums, ref List<List<int>> ans, int k) {
        if (k == nums.Length) {
            ans.Add(new List<int>(nums));
            return;
        }
        for (int i = k; i < nums.Length; i++) {
            int tmp = nums[i];
            nums[i] = nums[k];
            nums[k] = tmp;
            dfs(nums, ref ans, k+1);
            tmp = nums[i];
            nums[i] = nums[k];
            nums[k] = tmp;
        }
    }
}