1036 Boys vs Girls（排序）

红太狼 2024-04-08 12:43 22阅读 0赞

## 1036 Boys vs Girls（排序） ##

### 0、题目 ###

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 *g**r**a**d**e\*\*F*−*g**r**a**d**e\*\*M*. 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

### 1、大致题意 ###

给出 `N` 个同学的信息，输出女生中的最高分获得者的信息与男生中最低分获得者的信息，并输出他们的分数差。如果不存在女生或者男生，则对应获得者信息处输出`Absent`，而且差值处输出`NA`

### 2、基本思路 ###

设计结构体`Student`，然后`sort`大法

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

### 3、解题过程 ###

#### 3.1 `operator>` 的可疑问题（20/25） ####

首先第一份代码，写的很快，但是`测试点2`没过，很疑惑，感觉所有的点都考虑到了。

#include<vector>
    #include<iostream>
    #include<algorithm>
    using namespace std;
    
    struct Student {
        
    	string name;
    	string ID;
    	int grade;
    	bool operator>(const Student a) const {
         //这行有问题
    		if(grade!=a.grade) {
         //这行有问题
    			if(ID!=a.ID) {
         //这行有问题
    				return name>a.name; //这行有问题
    			} else //这行有问题
    				return ID>a.ID; //这行有问题
    		} else {
         //这行有问题
    			return grade>a.grade; //这行有问题
    		}
    	}
    } tmp;
    
    vector<Student>boys,girls;
    int main() {
        
    	int n;
    	char sex;
    	cin>>n;
    	for(int i=0; i<n; i++) {
        
    		cin>>tmp.name>>sex>>tmp.ID>>tmp.grade;
    		if(sex=='M') {
        
    			boys.push_back(tmp);
    		} else if(sex=='F') {
        
    			girls.push_back(tmp);
    		}
    	}
    	sort(girls.begin(),girls.end(),greater<Student>());
    	sort(boys.begin(),boys.end(),greater<Student>());
    	if(!girls.empty()) {
        
    		cout<<girls[0].name<<" "<<girls[0].ID<<endl;
    	} else {
        
    		cout<<"Absent"<<endl;
    	}
    	if(!boys.empty()) {
        
    		cout<<boys[boys.size()-1].name<<" "<<boys[boys.size()-1].ID<<endl;
    	} else {
        
    		cout<<"Absent"<<endl;
    	}
    	if(!girls.empty()&&!boys.empty()) {
        
    		int size=boys.size();
    		int gg=girls[0].grade-boys[size-1].grade;
    		cout<<gg;
    	} else {
        
    		cout<<"NA";
    	}
    	return 0;
    }

![在这里插入图片描述][d4b2160c1c7044f388e17ab3fd9a6ac2.png]

然后经过一系列的代码比对

发现如果不用 `operator>` 的重写，用`cmp`可以过的很轻松

#include<vector>
    #include<iostream>
    #include<algorithm>
    using namespace std;
    
    struct Student {
        
    	string name;
    	string ID;
    	int grade;
    	bool operator>(const Student a) const {
        
    //		if(grade>a.grade){
        
    //			return true;
    //		}else{
        
    //			return false;
    //		}
    		if(grade!=a.grade) {
         //这行有问题
    			if(ID!=a.ID) {
         //这行有问题
    				return name>a.name; //这行有问题
    			} else //这行有问题 
    				return ID>a.ID; //这行有问题
    		} else {
         //这行有问题
    			return grade>a.grade; //这行有问题
    		}
    	}
    } tmp;
    
    bool cmp1(Student s1,Student s2) {
        
    	if(s1.grade<s2.grade) {
        
    		return true;
    	} else {
        
    		return false;
    	}
    }
    
    bool cmp2(Student s1,Student s2) {
        
    	if(s1.grade>s2.grade) {
        
    		return true;
    	} else {
        
    		return false;
    	}
    }
    
    vector<Student>boys,girls;
    int main() {
        
    	int n;
    	char sex;
    	cin>>n;
    	for(int i=0; i<n; i++) {
        
    		cin>>tmp.name>>sex>>tmp.ID>>tmp.grade;
    		if(sex=='M') {
        
    			boys.push_back(tmp);
    		} else if(sex=='F') {
        
    			girls.push_back(tmp);
    		}
    	}
    //	sort(girls.begin(),girls.end(),greater<Student>());
    //	sort(boys.begin(),boys.end(),greater<Student>());
    	sort(girls.begin(),girls.end(),cmp2);
    	sort(boys.begin(),boys.end(),cmp1);
    	if(!girls.empty()) {
        
    		cout<<girls[0].name<<" "<<girls[0].ID<<endl;
    	} else {
        
    		cout<<"Absent"<<endl;
    	}
    	if(!boys.empty()) {
        
    		cout<<boys[boys.size()-1].name<<" "<<boys[boys.size()-1].ID<<endl;
    	} else {
        
    		cout<<"Absent"<<endl;
    	}
    	if(!girls.empty()&&!boys.empty()) {
        
    		int size=boys.size();
    		int gg=girls[0].grade-boys[size-1].grade;
    		cout<<gg;
    	} else {
        
    		cout<<"NA";
    	}
    	return 0;
    }

![在这里插入图片描述][e65772b16ea64d3eabd9481fdd52aa11.png]

直接AC，很奇怪，这两点有什么不同吗？经过排查发现下面的 `operator>` 就可以通过：

struct Student {
        
    	string name;
    	string ID;
    	int grade;
    	bool operator>(const Student a) const {
        
    		if(grade>a.grade){
        
    			return true;
    		}else{
        
    			return false;
    		}
    //		if(grade!=a.grade) { //这行有问题
    //			if(ID!=a.ID) { //这行有问题
    //				return name>a.name; //这行有问题
    //			} else //这行有问题
    //				return ID>a.ID; //这行有问题
    //		} else { //这行有问题
    //			return grade>a.grade; //这行有问题
    //		}
    	}
    } ;

就是不能写成注释的样子。可是题目中明确说明`It is guaranteed that all the grades are distinct.`

最后发现，我的 `operator>` 写的确实有问题。

struct Student {
        
    	string name;
    	string ID;
    	int grade;
    	bool operator>(const Student a) const {
        
    		if(grade==a.grade) {
         //注意这行
    			if(ID==a.ID) {
        
    				return ID>a.ID;
    			} else
    				return name>a.name;
    		} else {
        
    			if(grade>a.grade) {
        
    				return true;
    			} else {
        
    				return false;
    			}
    		}
    	}
    } ;

#### 3.2 AC代码 ####

#include<vector>
    #include<iostream>
    #include<algorithm>
    using namespace std;
    
    struct Student {
        
    	string name;
    	string ID;
    	int grade;
    	bool operator>(const Student a) const {
        
    		if(grade==a.grade) {
        
    			if(ID==a.ID) {
        
    				return ID>a.ID;
    			} else
    				return name>a.name;
    		} else {
        
    			if(grade>a.grade) {
        
    				return true;
    			} else {
        
    				return false;
    			}
    		}
    	}
    } tmp;
    
    vector<Student>boys,girls;
    int main() {
        
    	int n;
    	char sex;
    	cin>>n;
    	for(int i=0; i<n; i++) {
        
    		cin>>tmp.name>>sex>>tmp.ID>>tmp.grade;
    		if(sex=='M') {
        
    			boys.push_back(tmp);
    		} else if(sex=='F') {
        
    			girls.push_back(tmp);
    		}
    	}
    	sort(girls.begin(),girls.end(),greater<Student>());
    	sort(boys.begin(),boys.end(),greater<Student>());
    	if(!girls.empty()) {
        
    		cout<<girls[0].name<<" "<<girls[0].ID<<endl;
    	} else {
        
    		cout<<"Absent"<<endl;
    	}
    	if(!boys.empty()) {
        
    		cout<<boys[boys.size()-1].name<<" "<<boys[boys.size()-1].ID<<endl;
    	} else {
        
    		cout<<"Absent"<<endl;
    	}
    	if(!girls.empty()&&!boys.empty()) {
        
    		int size=boys.size();
    		int gg=girls[0].grade-boys[size-1].grade;
    		cout<<gg;
    	} else {
        
    		cout<<"NA";
    	}
    	return 0;
    }

![在这里插入图片描述][948d7b30f47842409e7018e702f15f91.png]

[d4b2160c1c7044f388e17ab3fd9a6ac2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/906f9dd369824fc49dda169bf5a9205c.png
[e65772b16ea64d3eabd9481fdd52aa11.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/65a4e6c9da184909803b92154ca4f78b.png
[948d7b30f47842409e7018e702f15f91.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/4a6f2f6830154b56b843d37cc1a3b948.png