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 (≤105 ) 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
题目解读
给出N个学生信息和一个数字C，每个学生的信息包括ID（6位数字），姓名（长度最多为8的字符串，无空格），分数（0-100）。根据数字C的取值，对学生信息按照不同策略进行排序，最终输出排序后的学生信息：
C=1：按 ID 递增； C=2：按姓名递增，如果同名，按ID递增； C=3：按分数递增，如果同分，按ID递增。
思路分析
这不就是三种排序策略就完了吗？
- 首先创建结构体
Student保存学生信息，注意name字段不要用string！！！，否则你最后一个测试点会是 运行超时，实际是内存溢出！
其实可以想想，题目给出说明姓名字段长度不超过10个字符，怎么可能没用呢，是吧！
- 如何排序，因为我们使用sort()函数对整个结构体数组进行排序，自己实现的比较函数只能是这样
int cmp(Student a, Student b)，所以我们要把C定义成一个全局变量，然后在这个函数中根据 C的取值进行不同的逻辑实现，当然你也可以实现三个比较函数，但我觉得没有必要。
代码
题目比较简单，代码注释也挺详细，没什么好说的。有个地方需要注意：学号是6位数字，输出必须用printf("d", id)格式化。
#include <iostream>
#include <algorithm>
#include <string.h>
using namespace std;
// 学生信息
struct Student {
int id, score;
// string name;
char name[10];
}stu[10001];
// 根据那个字段排序
int flag;
// 自定义比较函数
int cmp(Student a, Student b) {
// 按照ID递增
if (flag == 1) return a.id < b.id;
// 按照姓名自增
else if (flag == 2) {
// 重名就比较ID
if (strcmp(a.name, b.name) == 0) return a.id < b.id;
return strcmp(a.name, b.name) <= 0;
} else {
// 按照分数递增，相同就比较ID
return a.score != b.score ? a.score < b.score : a.id < b.id;
}
}
int main() {
// N 个学生
int n;
// 根据哪个字段排序
cin >> n >> flag;
// 读入学生信息
for (int i = 0; i < n; i) {
// cin >> stu[i].id >> stu[i].name >> stu[i].score;
scanf("%d %s %d", &stu[i].id, stu[i].name, &stu[i].score);
}
// 排序
sort(stu, stu n, cmp);
// 输出
for (int i = 0; i < n; i) {
// printf("d ", stu[i].id);
// cout << stu[i].name << " " << stu[i].score << endl;
printf("d %s %dn", stu[i].id, stu[i].name, stu[i].score);
}
return 0;
}
