Leetcode Combination Sum II

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Combination Sum II

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Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

Each number in C may only be used once in the combination.

Note:

  • All numbers (including target) will be positive integers.
  • Elements in a combination (a1a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
  • The solution set must not contain duplicate combinations.

For example, given candidate set 10,1,2,7,6,1,5 and target 8
A solution set is: 
[1, 7] 
[1, 2, 5] 
[2, 6] 
[1, 1, 6] 


标准递归回溯法可以搞定,防止重复,使用set容器。

class Solution {public:    vector<vector<int> > combinationSum2(vector<int> &num, int target) {sort(num.begin(), num.end());vector<int> tmp;set<vector<int> > rs;comb(rs, tmp, num, target);return vector<vector<int> >(rs.begin(), rs.end());}void comb(set<vector<int> > &rs, vector<int> &tmp, vector<int> &num, int tar, int index=0){if (!tmp.empty() && tar == 0) rs.insert(tmp);for (int i = index; i < num.size(); i++){if (tar < num[i]) return;tmp.push_back(num[i]);comb(rs, tmp, num, tar-num[i], i+1);tmp.pop_back();}}};






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