Problem Description：  

This time you are asked to tell the difference between the lowest grade of all the male students and the highest grade of all the female students.

Input Specification:

Each input file contains one test case. Each case contains a positive integer N, followed by N lines of student information. Each line contains a student's name, gender, ID and grade, separated by a space, where name and ID are strings of no more than 10 characters with no space, gender is either F(female) or M (male), and grade is an integer between 0 and 100. It is guaranteed that all the grades are distinct.

Output Specification:

For each test case, output in 3 lines. The first line gives the name and ID of the female student with the highest grade, and the second line gives that of the male student with the lowest grade. The third line gives the difference gradeF−gradeM. If one such kind of student is missing, output Absent in the corresponding line, and output NA in the third line instead.

Sample Input 1:

3
Joe M Math990112 89
Mike M CS991301 100
Mary F EE990830 95

Sample Output 1:

Mary EE990830
Joe Math990112
6

Sample Input 2:

1
Jean M AA980920 60

Sample Output 2:

Absent
Jean AA980920
NA

解题思路：

水题啊。根据性别来将男同学和女同学分别放入俩个vector中，然后将女生降序排列，男生升序排列。如果男生或女生的vector为空，就在相应的行输出"Absent"，男生最低分和女生最高分的差值就输出"NA"。否则输出男生最低分和女生最高分的同学姓名、学号，以及俩者的差值。

AC代码：

#include <bits/stdc++.h>
using namespace std;

struct stu
{
    string name;  //学生姓名
    char gender;  //学生性别
    string id;    //学生学号
    int grade;    //学生分数
};

bool fcmp(stu a,stu b)  //女学生降序排列
{
    return a.grade > b.grade;
}

bool mcmp(stu a,stu b)  //男学生升序排列
{
    return a.grade < b.grade;
}

int main()
{
    int N;
    cin >> N;
    vector<stu> male,female;  //男学生、女学生
    while(N--)
    {
        string name,id;
        char gender;
        int grade;
        cin >> name >> gender >> id >> grade;
        if(gender == 'M')  //男性
        {
            male.push_back({name,gender,id,grade});
        }
        else  //女性
        {
            female.push_back({name,gender,id,grade});
        }
    }
    int sum = 0;   //用来记录男女同学的差值
    if(female.empty())   //若没有输入女学生
    {
        cout << "Absent" << endl;
    }
    else
    {
        sort(female.begin(),female.end(),fcmp);
        cout << female[0].name << " " << female[0].id << endl;
        sum += female[0].grade;
    }
    if(male.empty())   //若没有输入男学生
    {
        cout << "Absent" << endl;
    }
    else
    {
        sort(male.begin(),male.end(),mcmp);
        cout << male[0].name << " " << male[0].id << endl;
        sum -= male[0].grade; 
    }
    if(!male.empty() && !female.empty())
    {
        cout << sum << endl;
    }
    else
    {
        cout << "NA" << endl;
    }
    return 0;
}