Combination Sum.cpp

class Solution {
public:
//global values shared between both functions
vector<vector<int>>result;
vector<int>current;
int sum;

void function(vector<int>& candidates,int target,int index)
{
    if(sum>target)return ;//base case if sum is greater then target then return 
    
    if(sum==target){
        result.push_back(current);//if sum is equal to target then just add current to result
    }
    for(int i=index;i<candidates.size();i++){
        sum+=candidates[i];//and current value to sum
        current.push_back(candidates[i]);//and current value to current vector
        function(candidates,target,i);//again reccure for same index i
        sum-=candidates[i];//back track mean remove value that previously added
        current.pop_back();//remove the value that previously added to current 
    }      
}

vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
    sum=0; 
    function(candidates,target,0);
    return result;
}
};