PAT Advanced 1028. List Sorting (25) (C语言实现)

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题目

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 $N$ ( $\le 10^5$ ) and $C$ , where $N$ is the number of records
and $C$ is the column that you are supposed to sort the records with. Then $N$
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 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

思路

应该也是很基本的排序。三种排序选项，后两个还有二级排序。也没有什么特殊的处理，所以很简单。

代码

最新代码@github，欢迎交流

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct {
    int ID;
    char name[9];
    int grade;
} Student, *pStudent;

/* increasing by ID */
int cmp1(const void *a, const void *b)
{
    pStudent s1 = *(pStudent*)a, s2 = *(pStudent*)b;
    return s1->ID - s2->ID;
}

/* non decreasing by name, then increasing by ID */
int cmp2(const void *a, const void *b)
{
    pStudent s1 = *(pStudent*)a, s2 = *(pStudent*)b;
    if(strcmp(s1->name, s2->name))
        return strcmp(s1->name, s2->name);
    else
        return s1->ID - s2->ID;
}

/* non decreasing by grade, then increasing by ID */
int cmp3(const void *a, const void *b)
{
    pStudent s1 = *(pStudent*)a, s2 = *(pStudent*)b;
    if(s1->grade - s2->grade)
        return s1->grade - s2->grade;
    else
        return s1->ID - s2->ID;
}

int main()
{
    int N, C;
    Student buffer[100000] = {0};
    pStudent students[100000] = {0}, *s = students;

    scanf("%d %d", &N, &C);
    for(int i = 0; i < N; i++, s++)
    {
        /* use a new struct buffer */
        *s = buffer + i;
        scanf("%d %s %d", &(*s)->ID, (*s)->name, &(*s)->grade);
    }

    if(C == 1)  /* increasing ID */
        qsort(students, N, sizeof(pStudent), cmp1);
    else if(C == 2)  /* non-decreasing name */
        qsort(students, N, sizeof(pStudent), cmp2);
    else  /* C == 3, non-decreasing grade */
        qsort(students, N, sizeof(pStudent), cmp3);

    for(int i = 0; i < N; i++)
        printf("%06d %s %d\n", students[i]->ID,
                               students[i]->name,
                               students[i]->grade);

    return 0;
}