LeetCode Subsets 系列

78. Subsets

Given a set of distinct integers, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: nums = [1,2,3]
Output:
[[3],[1],[2],[1,2,3],[1,3],[2,3],[1,2],[]]

class Solution {
public:
    void backtrack(vector<int>& nums,vector<vector<int>>& vv,vector<int>& v,int num)
    {
        if(num==nums.size())
        {
            vv.push_back(v);
            return;
        }
        v.push_back(nums[num]);
        backtrack(nums,vv,v,num+1);
        v.pop_back();
        backtrack(nums,vv,v,num+1);
    }
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<int> v;
        vector<vector<int>> vv;
        backtrack(nums,vv,v,0);
        return vv;
    }
};

90. Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: [1,2,2]
Output:
[[2],[1],[1,2,2],[2,2],[1,2],[]]

class Solution {
public:
    void backtrack(vector<int>& nums,vector<vector<int>>& vv,vector<int>& v,int num,int flag,int on)
    {
        if(num==nums.size())
        {
            vv.push_back(v);
            return;
        }
        if(on==0&&flag==1)
        {
            on=1; 
            if(num<nums.size()-1)
            {
                if(nums[num]==nums[num+1])
                    flag=1;
                else
                    flag=0;
            }
                backtrack(nums,vv,v,num+1,flag,0);
        }
        else
        { 
            if(num<nums.size()-1)
            {
                if(nums[num]==nums[num+1])
                    flag=1;
                else
                    flag=0;
            }
            v.push_back(nums[num]);
            backtrack(nums,vv,v,num+1,flag,1);
            v.pop_back();
            backtrack(nums,vv,v,num+1,flag,0);
        }
    }
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        vector<int> v;
        vector<vector<int>> vv;
        backtrack(nums,vv,v,0,-1,1);
        return vv;
    }
};