Intersection of Two Arrays II

题目：

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

Each element in the result should appear as many times as it shows in both arrays.

The result can be in any order.

分析：

分析可见Intersection of Two Arrays

解法：

class Solution {
public:
    /**
     * @param nums1 an integer array
     * @param nums2 an integer array
     * @return an integer array
     */
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        // Write your code here
        unordered_map<int, int> hash;
        vector<int> res;
        for (int i = 0; i < nums1.size(); i++) {
            if (hash.find(nums1[i]) == hash.end() ) {
                hash[nums1[i] ] = 1;
            } else {
                hash[nums1[i] ]++;
            }
        }
        for (int i = 0; i < nums2.size(); i++) {
            if (hash.find(nums2[i]) == hash.end() ) {
                continue;
            } else {
                res.push_back(nums2[i]);
                if (hash[nums2[i] ] == 1) {
                    hash.erase(nums2[i]);
                } else {
                    hash[nums2[i] ]--;
                }
            }
        }
        return res;
    }
};