LeetCode: Permutations II

一些小失误，基本一次过，这题可以明显看到自己的进步，map用得比较成熟了

 1 class Solution {

 2 public:

 3     void dfs(int dep, int maxdep, map<int, int> &s, vector<vector<int>> &ret, vector<int> &tmp) {

 4         if (dep == maxdep) {

 5             ret.push_back(tmp);

 6             return;

 7         }

 8         for (map<int, int>::iterator it = s.begin(); it != s.end(); it++) {

 9             int temp = it->first;

10             if (s[temp]) {

11                 s[temp]--;

12                 tmp.push_back(temp);

13                 dfs(dep+1, maxdep, s, ret, tmp);

14                 tmp.pop_back();

15                 s[temp]++;

16             }

17         }

18     }

19     vector<vector<int> > permuteUnique(vector<int> &num) {

20         // Start typing your C/C++ solution below

21         // DO NOT write int main() function

22         map<int, int> s;

23         sort(num.begin(), num.end());

24         int size = num.size();

25         for (int i = 0; i < size; i++) {

26             map<int, int>::iterator it;

27             it = s.find(num[i]);

28             if (it == s.end()) {

29                 s.insert(pair<int, int>(num[i], 1));

30             }

31             else s[num[i]]++;

32         }

33         vector<vector<int>> ret;

34         vector<int> tmp;

35         dfs(0, size, s, ret, tmp);

36         return ret;

37     }

38 };

 推荐下一段代码

 1 class Solution {

 2 public:

 3     void dfs(vector<int> &num, vector<vector<int> > &ans, int k) {

 4         if (k == num.size()) {

 5             ans.push_back(num);

 6             return;

 7         }

 8         set<int> visit;

 9         for (int i = k; i < num.size(); ++i) {

10             if (visit.find(num[i]) != visit.end()) continue;

11             swap(num[i], num[k]);

12             dfs(num, ans, k+1);

13             swap(num[i], num[k]);

14             visit.insert(num[i]);

15         }

16     }

17     vector<vector<int> > permuteUnique(vector<int> &num) {

18         vector<vector<int> > ans;

19         sort(num.begin(), num.end());

20         dfs(num, ans, 0);

21         return ans;

22     }

23 };

 C#

 1 public class Solution {

 2     public List<List<int>> PermuteUnique(int[] nums) {

 3         List<List<int>> ans = new List<List<int>>();

 4         Array.Sort(nums);

 5         dfs(nums, ref ans, 0);

 6         return ans;

 7     }

 8     public void dfs(int[] nums, ref List<List<int>> ans, int dep) {

 9         if (dep == nums.Length) {

10             ans.Add(new List<int>(nums));

11             return;

12         }

13         HashSet<int> visit = new HashSet<int>();

14         for (int i = dep; i < nums.Length; i++) {

15             if (visit.Contains(nums[i])) continue;

16             int tmp = nums[i];

17             nums[i] = nums[dep];

18             nums[dep] = tmp;

19             dfs(nums, ref ans, dep+1);

20             tmp = nums[i];

21             nums[i] = nums[dep];

22             nums[dep] = tmp;

23             visit.Add(nums[i]);

24         }

25     }

26 }

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