12.2-用sort对结构数组排序

     int strcmp( char* str1,char* str2)

     str1和str2可以是字符串常量或者字符串变量
    ①str1小于str2，返回-1；②str1等于str2，返回0；③str1大于str2，返回 1；

#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
struct Student{
	char name[20];
	int id;
	double gpa;
};
Student students[] = {
	{ "Jack", 112, 3.4 }, { "Mary", 102, 3.8 }, { "Mary",117,3.9 },
	{ "Ala", 333, 3.5 }, { "Zero",101,4.0 }
};
struct Rule1{   //按姓名从小到大排序
	bool operator()(const Student&s1, const Student&s2){
		if (strcmp(s1.name, s2.name) < 0)
			return  true;
		return false;
	}
};

void Print(Student a[], int size){
	for (int i = 0; i < size; i++)
		cout << a[i].name << " "<<a[i].id<<" "<<a[i].gpa;
	cout << endl;
}
int main(){
	int num = sizeof(students) / sizeof(Student);
	sort(students, students + num, Rule1());  //按姓名从小到大排序
	Print(students, num);
	cin.get(); 
	return 0;
}