1028. List Sorting (25)

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

Input

Each input file contains one test case. For each case, the first line contains two integers N (<=100000) and C, where N is the number of records and C is the column that you are supposed to sort the records with. Then N lines 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

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

最後一個點運行超時

import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

class Student{
	int sid;
	String sname;
	int score;
}
class SortByNumber_1 implements Comparator<Student>{
	//1，學號升序
	public int compare(Student o1, Student o2) {
		return o1.sid - o2.sid;
	}	
}
class SortByNumber_2 implements Comparator<Student>{
	//2，名字字母升序
	public int compare(Student o1, Student o2) {
		//如果字母相同，按學號升序
		if((o1.sname.charAt(0) - 48) == (o2.sname.charAt(0) - 48)){
			return o1.sid - o2.sid;
		}
		return (o1.sname.charAt(0) - 48) - (o2.sname.charAt(0) - 48);
	}
}
class SortByNumber_3 implements Comparator<Student>{
	//3，成績升序
	public int compare(Student o1, Student o2) {
		//如果成績相同，按學號升序
		if(o1.score == o2.score){
			return o1.sid - o2.sid;
		}
		return o1.score - o2.score;
	}
	
}
public class Main{

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int sum = in.nextInt(),charge = in.nextInt();
		Student[] stu = new Student[sum];
		for ( int i = 0; i < sum; i++ ){
			stu[i] = new Student();
			stu[i].sid = in.nextInt();
			stu[i].sname = in.next();
			stu[i].score = in.nextInt();
		}
		switch (charge) {
		case 1:
			SortByNumber_1 sb_1 = new SortByNumber_1();
			Arrays.sort(stu,sb_1);
			break;
		case 2:
			SortByNumber_2 sb_2 = new SortByNumber_2();
			Arrays.sort(stu,sb_2);
			break;
		case 3:
			SortByNumber_3 sb_3 = new SortByNumber_3();
			Arrays.sort(stu,sb_3);
			break;
		}
		for ( int i = 0; i < sum; i++ ){
			System.out.printf("%06d",stu[i].sid);
			System.out.println(" "+stu[i].sname+" "+stu[i].score);
		}
	}

}

升序：o1.sid-o2.sid

降序：o2.sid-o1.sid

注意：

for ( int i = 0; i < sum; i++ ){
			stu[i] = new Student();
			stu[i].sid = in.nextInt();
			stu[i].sname = in.next();
			stu[i].score = in.nextInt();
		}

stu[i] = new Student();

new數組的時候並沒有實例化stu[i],如果不實例化stu[i],會空指針異常

參考：http://www.2cto.com/kf/201504/395324.html