LeetCode347. Top K Frequent Elements

先利用map统计各数的个数，再用vector存储统计结果，自定义vector排序

class Solution {
public:
vector<int> topKFrequent(vector<int>& nums, int k) {
vector<int> m;
if(k>=nums.size()) return nums;
map<int,int> cnt;
for(vector<int>::iterator it=nums.begin();it!=nums.end();it++){
cnt[*it]++;
}
vector<pair<int,int> > rs;
for(map<int,int>::iterator it=cnt.begin();it!=cnt.end();it++){
rs.push_back(*it);
}
sort(rs.begin(),rs.end(),[&](pair<int,int> a,pair<int,int> b){return a.second > b.second;});
int i=0;
for(vector<pair<int,int> >::iterator it=rs.begin();it!=rs.end(),i!=k;++it,++i){
m.push_back(it->first);
}
return m;
}
};