题目描述
Given a list of N student records with name, ID and grade. You are supposed to sort the records with respect to the grade in non-increasing order, and output those student records of which the grades are in a given interval.

输入描述:
Each input file contains one test case. Each case is given in the following format:
N
name[1] ID[1] grade[1]
name[2] ID[2] grade[2]
... ...
name[N] ID[N] grade[N]
grade1 grade2

where name[i] and ID[i] are strings of no more than 10 characters with no space, grade[i] is an integer in [0, 100], grade1 and grade2 are the boundaries of the grade's interval. It is guaranteed that all the grades are distinct.

输出描述:
For each test case you should output the student records of which the grades are in the given interval [grade1, grade2] and are in non-increasing order. Each student record occupies a line with the student's name and ID, separated by one space. If there is no student's grade in that interval, output "NONE" instead.

输入例子:
4
Tom CS000001 59
Joe Math990112 89
Mike CS991301 100
Mary EE990830 95
60 100

输出例子:
Mike CS991301
Mary EE990830
Joe Math990112

代码：

#include<iostream>
#include<string>

using namespace std;

struct student
{
    string name;
    string ID;
    int grade;
};

void swap(student *a, student *b)   // 交换
{
    student *c = NULL;
    c=a;
    a=b;
    b=c;
}

int main()
{
    // freopen("input.txt", "r", stdin);

    int number; // 输入数字以字符串形式记录
    cin >> number;
    
    student *Stu = new student[number]; // 动态分配空间
    for (int i=0; i<number; i++)
    {
        cin >> Stu[i].name >> Stu[i].ID >> Stu[i].grade;
    }

    int grade1, grade2;
    cin >> grade1 >> grade2;

    for (int i=0; i<number; i++)    // 冒泡排序
    {
        for (int j=i+1; j<number; j++)
        {
            if (Stu[i].grade < Stu[j].grade)
            {
                swap(Stu[i], Stu[j]);
            }
        }
    }

    int counter = 0;
    for (int i=0; i<number; i++)
    {
        if (Stu[i].grade >= grade1 && Stu[i].grade <= grade2)
        {
            cout << Stu[i].name << " " << Stu[i].ID << endl;
            counter ++;
        }
        if (i == number-1 && 0 == counter)
        {
            cout << "NONE" << endl;
        }
    }

    delete[] Stu;
    return 0;
}

这一题比较简单，有很多种实现方法。
Tips：

1. 动态分配空间或者vector.push_back都可以
2. 自己写排序+swap，当然也可以调用algorithm库中的cmp+sort
3. 先排序再筛选更耗时，反之更占内存。