No.178 - LeetCode1311

pair数组排序默认按first升序

class Solution {
public:
    vector<string> watchedVideosByFriends(vector<vector<string>>& watchedVideos, vector<vector<int>>& friends, int id, int level) {
        int N = friends.size();
        vector<vector<int>> E(N,vector<int>());
        for(int i=0;i<N;i++){
            for(int j=0;j<friends[i].size();j++){
                E[i].push_back(friends[i][j]);
                E[friends[i][j]].push_back(i);
            }
        }
        map<string,int> mp;
        vector<int> color(N,-1);
        color[id] = 0;
        queue<int> q;
        q.push(id);
        while(!q.empty()){
            int now = q.front();
            q.pop();
            if(color[now] == level){
                for(int i=0;i<watchedVideos[now].size();i++){
                    mp[watchedVideos[now][i]] ++ ;
                }
                continue;
            }
            for(int i=0;i<E[now].size();i++){
                if(color[E[now][i]] == -1){
                    color[E[now][i]] = color[now] + 1;
                    q.push(E[now][i]);
                }
            }
        }
        vector<pair<int,string>> T;
        for(map<string,int>::iterator p=mp.begin();p!=mp.end();p++){
            T.push_back(make_pair(p->second,p->first));
        }
        sort(T.begin(),T.end());
        vector<string> ans;
        for(int i=0;i<T.size();i++){
            ans.push_back(T[i].second);
        }
        return ans;
    }
};