LeetCode OJ---1. Two Sum

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].

class Solution
{
public:
vector<int> twoSum(vector<int>& nums, int target)
{
unordered_map<int, int> um;
for (int i = 0; i < nums.size(); i++)
{
int cur_value = nums[i];
if (um.count(target - cur_value)>0)
return vector<int> {um[target - cur_value], i};
um[cur_value] = i;
}
return vector<int>(0);
}
};