Two Sum

 https://leetcode.com/problems/two-sum/

1st soln(brute force) using 2 for loops o[n^2]

2nd soln (using hash)

 

vector<int> ans;
        unordered_map<int,int>mp;
        for(int i=0;i<nums.size();i++)
        {
            if(mp.find(target-nums[i])!=mp.end())
            {
                ans.push_back(mp[target-nums[i]]);
                ans.push_back(i);
                return ans;
            }
            mp[nums[i]]=i;
        }
        return ans;

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