Two sum

Posted 2022-11-01 hujianglang

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

//method1:
class Solution
    public:
        vector<int> twoSum(vector<int>& nums, int target)
            unordered_map<int,int> m;
            vector<int> res;
            for(int i = 0; i < nums.size(); ++i)
                m[nums[i]] = i;
            
            
            for(int i = 0; i < nums.size(); ++i)
                int t = target - nums[i];
                if(m.count(t) && m[t] != i)
                    res.push_back(i);
                    res.push_back(m[t]);
                    break;
                
            
            return res;
        
;

//method2:
class Solution2
    public:
        vector<int> twoSum(vector<int>& nums, int target)
            unordered_map<int,int> m;
            for(int i = 0; i < nums.size(); ++i)
                if(m.count(target - nums[i]))
                    return i,m[target - nums[i]];
                
                m[nums[i]] = i;
            
            return ;
        
;