LeetCode Problems

2sum.cpp

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        map<int,int> m;
        vector<int> v;
        for(int i=0;i<nums.size();i++)
        {
            if(m.find(target-nums[i])!=m.end())
            {
                v.push_back(m[target-nums[i]]);
                v.push_back(i);
            }
            else
            {
                m[nums[i]]=i;
            }
        }
        return v;
    }
    
};

2sumII.cpp

//Two Sum II - Input array is sorted

class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
        int low=0;
        int high=numbers.size()-1;
        //vector<int> v(2);
        while(low<high)
        {
            //int sum=numbers[low]+numbers[high];
            if((numbers[low]+numbers[high])==target)
            {
                return {low+1,high+1};
            }
            else if((numbers[low]+numbers[high])>target)
            {
                high--;
            }
            else
            {
                low++;
            }
        }
        return {};
    }
};

3sum.cpp

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        set<vector<int> > st;
        sort(num.begin(), num.end());
        int i, j, k;
        int n = num.size();
        for (i = 0; i < n - 2; i++) {
            j = i+1;
            k = n-1;
            while (j < k) {
                int sum = num[i] + num[j] + num[k];
                if (sum == 0) {
                    vector<int> v;
                    v.push_back(num[i]);
                    v.push_back(num[j]);
                    v.push_back(num[k]);
                    st.insert(v);
                    j++;
                    k--;
                } else if (sum > 0) {
                    k--;
                } else if (sum < 0) {
                    j++;
                }
            }
        }
        vector<vector <int> >result (st.begin(), st.end());
        return result;
    }
};