1. Two Sum

Total Accepted: 238787 Total Submissions: 999694 Difficulty: Easy

 

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.

Example:

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

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

 

UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.

 

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class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> v = nums;
        vector<int> w;
        sort(nums.begin(), nums.end());
        int i = 0, j = nums.size() - 1;
        while (i < j){
            if (nums[i] + nums[j] == target){
                for (int m = 0; m < v.size(); m++){
                    if (v[m] == nums[i]){
                        w.push_back(m);
                        continue;
                    }
                    if (v[m] == nums[j]){
                        w.push_back(m);
                    }
                }
                sort(w.begin(), w.end());
                break;
            }
            else if (nums[i] + nums[j] < target){
                i++;
            }
            else{
                j--;
            }
        }
        return w;
    }
};

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