Leetcode: Subsets II

最新推荐文章于 2019-07-27 20:45:00 发布

原创最新推荐文章于 2019-07-27 20:45:00 发布 · 743 阅读

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本文深入探讨了如何使用递归和回溯技术解决LeetCode中子集II问题，通过先排序输入集合，然后巧妙地利用元素重复性进行剪枝，提高算法效率。文中详细解释了算法实现过程，并提供了关键代码片段，帮助读者理解和实现解决方案。

http://oj.leetcode.com/problems/subsets-ii/

class Solution {
public:
    // First, we sort the input set
    // Second, whenever we have a new element, we count the number of this element
    // Third, we enumerate how many elements we put into the current selection
    vector<vector<int> > res;
    void subsetsWithDupHelper(vector<int> &S, vector<int> current, int pos){
        if(pos==S.size()){
            res.push_back(current);
            return;
        }
        
        int cnt=1;
        while((pos+cnt)<S.size()&&S[pos]==S[pos+cnt]) cnt++;
        for(int i=0;i<=cnt;i++){
            subsetsWithDupHelper(S,current,pos+cnt);
            current.push_back(S[pos]);
        }
    }
    vector<vector<int> > subsetsWithDup(vector<int> &S) {
        res.clear();
        sort(S.begin(),S.end());
        subsetsWithDupHelper(S, vector<int>(), 0);
        return res;
    }
};