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Two Sum

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Description

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

Solution

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class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<int> ret;
        if (nums.size() < 2) return ret;
        unordered_map<int, int> mapping;
        for (int i = 0; i < nums.size(); ++i) mapping[nums[i]] = i;
        for (int i = 0; i < nums.size(); ++i) {
            if(mapping.count(target - nums[i]) == 0 || mapping[target - nums[i]] == i) continue;
            ret.push_back(i);
            ret.push_back(mapping[target - nums[i]]);
            return ret;
        }
        return ret;
    }
};