1.for循环遍历

class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        int cnt=0;
        for(auto i=nums.begin();i<nums.end();++i)
            if(*i==k)
                cnt++;
        return cnt;
    }
};

2.multiset count

class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        multiset<int> ans;
        for(auto i : nums)
            ans.insert(i);
        return ans.count(k);
    }
};

3.lower_bound,upper_bound

class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        auto l = lower_bound(nums.begin(), nums.end(), k);
        auto r = upper_bound(nums.begin(), nums.end(), k);
        return r-l;
    }
};

4.count

class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        return count(nums.begin(), nums.end(), k);
    }
};