【PAT】1028. List Sorting (25)

题目链接：http://pat.zju.edu.cn/contests/pat-a-practise/1028

题目描述：

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

---

分析：

输入学生信息，按照指定项进行排序。当按照name或grade排序时如果存在一样的情况就按照学号递增的形式输出。

原本是想用c++做，num和name用string类型表示。但是用c++中的cin进行输入时会有一组数据在最终提交时超时。所以改用scanf输入。

由于scanf不能输入string类型，所以将string类型用char[]代替。

但是如果num和name都用char[]类型，在输出时又会出错，见“错误代码一”。

后面就将num为int型，为了满足num为6位的要求，要用printf("%06d",num) 这种形式输出。

错误代码一：

#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<vector>
#include<cstdio>
using namespace std;

typedef struct student
{
    char num[6];
    char name[20];
    int grade;
}Student;

int n;
bool comparison(Student a,Student b)
{
    if(n==1)
    {
        return strcmp(a.num,b.num)<0;
    }
    else if(n==2)
    {        
        if(strcmp(a.name,b.name) == 0)
            return strcmp(a.num,b.num);
        return strcmp(a.name,b.name)<0;
    }
    else if(n==3)
    {
        if(a.grade == b.grade)
            return strcmp(a.num,b.num) < 0;    
        return a.grade < b.grade;
    }        
}

int main()
{
    int M;
    cin>>M>>n;
    vector<Student> s(M);
    int i;
    for(i=0; i<M; i++)
        //cin>>s[i].num>>s[i].name>>s[i].grade;
        scanf("%s%s%d",&s[i].num,&s[i].name,&s[i].grade);

    sort(s.begin(),s.end(),comparison);
    for(i=0; i<M; i++)
        cout<<s[i].num<<" "<<s[i].name<<" "<<s[i].grade<<endl;

    return 0;
}

最终的输出不正确。但是
原因是？？？

正确代码：

参考：http://blog.csdn.net/sunbaigui/article/details/8657115

#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<vector>
#include<cstdio>
using namespace std;

typedef struct student
{
	int num;
	char name[20];
	int grade;
}Student;

int n;
bool comparison(Student a,Student b)
{
	if(n==1)
	{
		return a.num<b.num;
	}
	else if(n==2)
	{
		if(strcmp(a.name,b.name) == 0)
			return a.num<b.num;
		return strcmp(a.name,b.name)<0;
	}
	else if(n==3)
	{
		if(a.grade == b.grade)
			return a.num<b.num;
		return a.grade < b.grade;
	}
}

int main()
{
	int M;
	cin>>M>>n;
	vector<Student> s(M);
	int i;
	for(i=0; i<M; i++)
		scanf("%d%s%d",&s[i].num,&s[i].name,&s[i].grade);

	sort(s.begin(),s.end(),comparison);
	for(i=0; i<M; i++)
		printf("%06d %s %d\n",s[i].num,s[i].name,s[i].grade);

	return 0;
}