# Combination Sum II Problem

## Description

LeetCode Problem 40.

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

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

Note: The solution set must not contain duplicate combinations.

Example 1:

``````1
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Input: candidates = [10,1,2,7,6,1,5], target = 8
Output:
[
[1,1,6],
[1,2,5],
[1,7],
[2,6]
]
``````

Example 2:

``````1
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Input: candidates = [2,5,2,1,2], target = 5
Output:
[
[1,2,2],
[5]
]
``````

Constraints:

• 1 <= candidates.length <= 100
• 1 <= candidates[i] <= 50
• 1 <= target <= 30

## Sample C++ Code

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

void dfs(vector<int>& candidates, vector<int>& comb, int target, int idx) {
if (target == 0)
ans.push_back(comb);
if (target <= 0)
return;

for (int i = idx; i < candidates.size(); i ++) {
if (i > idx && candidates[i] == candidates[i-1])
continue;
if (target >= candidates[i]) {
comb.push_back(candidates[i]);
dfs(candidates, comb, target-candidates[i], i+1);
comb.pop_back();
}
}
return;
}

vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
vector<int> comb;
sort(candidates.begin(), candidates.end());
dfs(candidates, comb, target, 0);
return ans;
}
};
``````