LeetCode 78. Subsets

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

Note: 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],
[]
]

题目大意：给一个集合nums，求nums的所有子集集合～

分析：用位运算，j从0到maxn变化，每一次计算j移动i位后最后一位是否为1，如果为1就将nums[i]的值放入result[j]～

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        int len = nums.size();
        int maxn = pow(2, len);
        vector<vector<int>> result(maxn);
        for (int i = 0; i < len; i++) {
            for (int j = 0; j < maxn; j++) {
                if ((j >> i) & 1)
                    result[j].push_back(nums[i]);
            }
        }
        return result;
    }
};

class Solution {

public:

vector<vector<int>> subsets(vector<int>& nums) {

int len = nums.size();

int maxn = pow(2, len);

vector<vector<int>> result(maxn);

for (int i = 0; i < len; i++) {

for (int j = 0; j < maxn; j++) {

if ((j >> i) & 1)

result[j].push_back(nums[i]);

}

return result;

}

};