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349. 两个数组的交集

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349. 两个数组的交集

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class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        vector<int> ret;
        unordered_set<int> set(nums2.begin(), nums2.end());
        unordered_set<int> set2;
        for(auto& num : nums1)
        {
            if(set.count(num) && set2.emplace(num).second)
                ret.push_back(num);
        }
        return ret;
    }
};
双指针

主要是省空间

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class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        int length1 = nums1.size();
        int length2 = nums2.size();
        sort(nums1.begin(), nums1.end());
        sort(nums2.begin(), nums2.end());
        int i = 0, j = 0;
        vector<int> ret;
        while(i < length1 && j < length2)
        {
            if(nums1[i] == nums2[j])
            {
                if(ret.empty() || nums1[i] != ret.back())
                    ret.push_back(nums1[i]);
                ++i;
                ++j;
            }else if(nums1[i] < nums2[j])
                ++i;
            else
                ++j;
        }
        return ret;
    }
};