leetcode:Combination Sum II

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 (a1, a2,
… , 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]

class Solution {
public:
vector<vector<int> > combinationSum2(vector<int> &num, int target) {
sort(num.begin(),num.end());
vector<vector<int> > result;
vector<int> pre;
generate(num,0,pre,target,0,result);
return result;
}

void generate(vector<int> & num, int idx, vector<int> & pre, int target, int sum, vector<vector<int> > & result)
{
int n = num.size();
if(sum > target)
return;
if(sum == target)
{
result.push_back(pre);
return;
}
if(idx >= n)
return;
pre.push_back(num[idx]);
generate(num,idx+1,pre,target,sum+num[idx],result);
pre.pop_back();
int i = idx;
while(idx < n && num[i] == num[idx])
idx++;
generate(num,idx,pre,target,sum,result);
}
};