349. Intersection of Two Arrays

Problem:

Given two arrays, write a function to compute their intersection.

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [9,4]

Note:

• Each element in the result must be unique.
• The result can be in any order.

思路：

Solution (C++):

vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
    set<int> s;
    vector<int> res{};
    int m = nums1.size(), n = nums2.size();
    if (m == 0 || n == 0)  return res;
    sort(nums1.begin(), nums1.end());
    sort(nums2.begin(), nums2.end());
    if (m <= n) {
        for (int i = 0; i < m; ++i)
            if (binarySearch(nums2, nums1[i])) s.insert(nums1[i]);
    }
    else {
        for (int i = 0; i < n; ++i) {
            if (binarySearch(nums1, nums2[i]))  s.insert(nums2[i]);
        }
    }
    for (auto x : s) res.push_back(x);
    return res;
}
bool binarySearch(vector<int>&  v, int num) {
    int l = 0, r = v.size()-1, mid;
    while (l <= r) {
        mid = l + (r-l) / 2;
        if (num == v[mid])  return true;
        else if (num < v[mid])  r = mid - 1;
        else l = mid + 1;
    }
    return false;
}

性能：

Runtime: 8 ms  Memory Usage: 6.9 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB