Qualifying Contest
Very soon Berland will hold a School Team Programming Olympiad. From each of the mBerland regions a team of two people is invited to participate in the olympiad. The qualifying contest to form teams was held and it was attended by n Berland students. There were at least two schoolboys participating from each of the m regions of Berland. The result of each of the participants of the qualifying competition is an integer score from 0 to 800 inclusive.
The team of each region is formed from two such members of the qualifying competition of the region, that none of them can be replaced by a schoolboy of the same region, not included in the team and who received a greater number of points. There may be a situation where a team of some region can not be formed uniquely, that is, there is more than one school team that meets the properties described above. In this case, the region needs to undertake an additional contest. The two teams in the region are considered to be different if there is at least one schoolboy who is included in one team and is not included in the other team. It is guaranteed that for each region at least two its representatives participated in the qualifying contest.
Your task is, given the results of the qualifying competition, to identify the team from each region, or to announce that in this region its formation requires additional contests.
Input
The first line of the input contains two integers n and m (2 ≤ n ≤ 100 000, 1 ≤ m ≤ 10 000, n ≥ 2m) — the number of participants of the qualifying contest and the number of regions in Berland.
Next n lines contain the description of the participants of the qualifying contest in the following format: Surname (a string of length from 1 to 10 characters and consisting of large and small English letters), region number (integer from 1 to m) and the number of points scored by the participant (integer from 0 to 800, inclusive).
It is guaranteed that all surnames of all the participants are distinct and at least two people participated from each of the m regions. The surnames that only differ in letter cases, should be considered distinct.
Output
Print m lines. On the i-th line print the team of the i-th region — the surnames of the two team members in an arbitrary order, or a single character "?" (without the quotes) if you need to spend further qualifying contests in the region.
Examples
5 2
Ivanov 1 763
Andreev 2 800
Petrov 1 595
Sidorov 1 790
Semenov 2 503
Sidorov Ivanov
Andreev Semenov
5 2
Ivanov 1 800
Andreev 2 763
Petrov 1 800
Sidorov 1 800
Semenov 2 503
?
Andreev Semenov
Note
In the first sample region teams are uniquely determined.
In the second sample the team from region 2 is uniquely determined and the team from region 1 can have three teams: "Petrov"-"Sidorov", "Ivanov"-"Sidorov", "Ivanov" -"Petrov", so it is impossible to determine a team uniquely.
sol：STL非常好用，按照分数从大到小排序后如果第二名分数和第三名相同就无法确定了
#include <bits/stdc++.h> using namespace std; typedef int ll; inline ll read() { ll s=0; bool f=0; char ch=' '; while(!isdigit(ch)) { f|=(ch=='-'); ch=getchar(); } while(isdigit(ch)) { s=(s<<3)+(s<<1)+(ch^48); ch=getchar(); } return (f)?(-s):(s); } #define R(x) x=read() inline void write(ll x) { if(x<0) { putchar('-'); x=-x; } if(x<10) { putchar(x+'0'); return; } write(x/10); putchar((x%10)+'0'); return; } #define W(x) write(x),putchar(' ') #define Wl(x) write(x),putchar('\n') const int N=10005,B=15; int n,m; struct Record { char Name[B]; int Score; }; inline bool cmp(Record p,Record q) { return p.Score>q.Score; } vector<Record>Vec[N]; char Name[B]; int main() { int i; R(n); R(m); for(i=1;i<=n;i++) { Record tmp; int id; scanf("%s",tmp.Name); R(id); R(tmp.Score); Vec[id].push_back(tmp); } for(i=1;i<=m;i++) { sort(Vec[i].begin(),Vec[i].end(),cmp); if(Vec[i].size()==1) { puts("?"); } else if(Vec[i].size()==2) { printf("%s",Vec[i][0].Name); putchar(' '); printf("%s",Vec[i][1].Name); putchar('\n'); } else { if(Vec[i][1].Score==Vec[i][2].Score) puts("?"); else { printf("%s",Vec[i][0].Name); putchar(' '); printf("%s",Vec[i][1].Name); putchar('\n'); } } } return 0; } /* input 5 2 Ivanov 1 763 Andreev 2 800 Petrov 1 595 Sidorov 1 790 Semenov 2 503 output Sidorov Ivanov Andreev Semenov input 5 2 Ivanov 1 800 Andreev 2 763 Petrov 1 800 Sidorov 1 800 Semenov 2 503 output ? Andreev Semenov */