[Leetcode]Subsets

Subsets My Submissions Question

Total Accepted: 72388 Total Submissions: 247343 Difficulty: Medium

Given a set of distinct integers, nums, return all possible subsets.

Note:

Elements in a subset must be in non-descending order.

The solution set must not contain duplicate subsets.

For example,

If nums = [1,2,3], a solution is:

[

[3],

[1],

[2],

[1,2,3],

[1,3],

[2,3],

[1,2],

[]

]

Subscribe to see which companies asked this question

我是按照我博客里那种方法做的，有些地方不太一样，用adapter模式（允许我装个逼）搞一下，结果对顺序还有要求。。。干脆每次插入都排个序，这样时间就上去了，12ms。如果不排序就要修改一下getSubstring（）这个就行，可是我懒得修改了。当然用DFS做也没问题，就比较简单了。下面把两种方法都贴出来

class Solution {
public:
vector<vector<int>> subsets(vector<int>& nums) {
int len = nums.size();
string str;
for(int i = 0;i != len;++i){
str.push_back(nums[i] + '0');
}

vector<string> res = func(str);

vector<vector<int> >    ans;
ans.push_back({});
for(int i = 0;i != res.size();++i){
vector<int> tem;
for(int j = 0;j != res[i].size();++j){
tem.push_back(res[i][j] - '0');
}
sort(tem.begin(),tem.end());
ans.push_back(tem);
}
sort(ans.begin(),ans.end());
return ans;
}

vector<string> func(string str){
int len = str.size();
vector<string>  res;
int num = 1 << len;
num = num - 1;
//cout << num << endl;
for(int i = 1;i <= num;++i){
string tem = getSubstring(str,i);
res.push_back(tem);
}
return res;
}
string getSubstring(string str,int num){
string tem;
//cout << num << endl;
int len = str.size();
int n = len - 1;
while(num){
if(num & 0x1){
tem += str
;
}
num = num >> 1;
--n;
}
return tem;
}
};

DFS:

class Solution {
public:
vector<vector<int>> subsets(vector<int>& nums) {
sort(nums.begin(), nums.end());
vector<vector<int>> res;
vector<int> path;
dfs(nums, 0, path, res);
return res;
}

void dfs(vector<int>& nums, int index, vector<int>& path, vector<vector<int>>& res) {
res.push_back(path);
for (unsigned int i = index; i < nums.size(); i++) {
path.push_back(nums[i]);
dfs(nums, i+1, path, res);
path.pop_back();
}
}
};