Leetcode 78. 子集 && 90. 子集 II

Leetcode 78. 子集

回溯

class Solution {
public:

    vector<vector<int>> ans;
    vector<int> path;

    void dfs(vector<int>& nums, int start) {
        // if (start == nums.size()) {
        //     ans.push_back(path);
        //     return ;
        // }
        ans.push_back(path);
        
        for (int i = start; i < nums.size(); i++) {
            path.push_back(nums[i]);
            dfs(nums, i + 1);
            path.pop_back();
        }
    }

    vector<vector<int>> subsets(vector<int>& nums) {
        dfs(nums, 0);
        return ans;

    }
};
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Leetcode 90. 子集 II

回溯+剪枝

class Solution {
public:
    vector<vector<int>> ans;
    vector<int> path;

    void dfs(vector<int>& nums, int start) {
        ans.push_back(path);

        for (int i = start; i < nums.size(); i++) {
            // 剪枝
            if (i > start && nums[i] == nums[i - 1])
                continue;
            path.push_back(nums[i]);
            dfs(nums, i + 1);
            path.pop_back();
        }
    }

    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        dfs(nums, 0);
        return ans;
    }
};
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