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

class Solution {
public:
    void dfs(int dep, int maxdep, map<int, int> &s, vector<vector<int>> &ret, vector<int> &tmp) {
        if (dep == maxdep) {
            ret.push_back(tmp);
            return;
        }
        for (map<int, int>::iterator it = s.begin(); it != s.end(); it++) {
            int temp = it->first;
            if (s[temp]) {
                s[temp]--;
                tmp.push_back(temp);
                dfs(dep+1, maxdep, s, ret, tmp);
                tmp.pop_back();
                s[temp]++;
            }
        }
    }
    vector<vector<int> > permuteUnique(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        map<int, int> s;
        sort(num.begin(), num.end());
        int size = num.size();
        for (int i = 0; i < size; i++) {
            map<int, int>::iterator it;
            it = s.find(num[i]);
            if (it == s.end()) {
                s.insert(pair<int, int>(num[i], 1));
            }
            else s[num[i]]++;
        }
        vector<vector<int>> ret;
        vector<int> tmp;
        dfs(0, size, s, ret, tmp);
        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;
        }
        set<int> visit;
        for (int i = k; i < num.size(); ++i) {
            if (visit.find(num[i]) != visit.end()) continue;
            swap(num[i], num[k]);
            dfs(num, ans, k+1);
            swap(num[i], num[k]);
            visit.insert(num[i]);
        }
    }
    vector<vector<int> > permuteUnique(vector<int> &num) {
        vector<vector<int> > ans;
        sort(num.begin(), num.end());
        dfs(num, ans, 0);
        return ans;
    }
};

 C#

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