Excel can sort records according to any column. Now you are supposed to imitate this function.

Input Specification:

Each input file contains one test case. For each case, the first line contains two integers N (≤10​5​​) and C, where N is the number of records and C is the column that you are supposed to sort the records with. Then Nlines follow, each contains a record of a student. A student's record consists of his or her distinct ID (a 6-digit number), name (a string with no more than 8 characters without space), and grade (an integer between 0 and 100, inclusive).

Output Specification:

For each test case, output the sorting result in N lines. That is, if C = 1 then the records must be sorted in increasing order according to ID's; if C = 2 then the records must be sorted in non-decreasing order according to names; and if C = 3 then the records must be sorted in non-decreasing order according to grades. If there are several students who have the same name or grade, they must be sorted according to their ID's in increasing order.

Sample Input 1:

3 1
000007 James 85
000010 Amy 90
000001 Zoe 60

Sample Output 1:

000001 Zoe 60
000007 James 85
000010 Amy 90

Sample Input 2:

4 2
000007 James 85
000010 Amy 90
000001 Zoe 60
000002 James 98

Sample Output 2:

000010 Amy 90
000002 James 98
000007 James 85
000001 Zoe 60

Sample Input 3:

4 3
000007 James 85
000010 Amy 90
000001 Zoe 60
000002 James 90

Sample Output 3:

000001 Zoe 60
000007 James 85
000002 James 90
000010 Amy 90
  
#include <stdio.h>
#include <algorithm>
#include <string>
#include <iostream>
using namespace std;
const int maxn=100010;
struct stu{
  string id;
  string name;
  int grade;
}students[maxn];
bool cmp1(stu s1,stu s2){
  return s1.id<s2.id;
}
bool cmp2(stu s1,stu s2){
  if(s1.name==s2.name)  return s1.id<s2.id;
  else return s1.name<s2.name;
}
bool cmp3(stu s1,stu s2){
  if(s1.grade==s2.grade)  return s1.id<s2.id;
  else return s1.grade<s2.grade;
}
int main(){
  int n,c;
  scanf("%d %d",&n,&c);
  for(int i=0;i<n;i++){
    cin>>students[i].id>>students[i].name>>students[i].grade;
  }
  if(c==1){
    sort(students,students+n,cmp1);
  }
  else if(c==2){
    sort(students,students+n,cmp2);
  }
  else if(c==3){
    sort(students,students+n,cmp3);
  }
  for(int i=0;i<n;i++){
    printf("%s %s %d\n",students[i].id.c_str(),students[i].name.c_str(),students[i].grade);
  }
}

注意点：很简单的排序题，但是最后一个测试点会超时，原因是cout很慢，一开始以为是sort很慢，想是不是要用priority_queue，发现一样超时。然后把id改成int试了试还是超时，百度了一下，发现人家也都是sort做的唯一不同输出name也用printf。最后果然是cout速度太慢，printf输出string要用c_str。