二分查找法

#include <iostream>
using namespace std;
class Person{
	string name;
	int age;
	string addr;
public:
	Person(const char* n, int a, const char* ad)
	:name(n),age(a),addr(ad){}
	friend bool operator<(const Person& a, const Person& b){
		return a.name<b.name;
	}
	friend bool operator==(const Person& a, const Person& b){
		return a.name==b.name;
	}
	friend ostream& operator<<(ostream& o, const Person& a){
		o << a.name << ':' << a.age << ',' << a.addr;
		return o;
	}
};
/*Person* binarysearch(Person* a, int n, const string& name)
{
	if(n<=0) return NULL;
	int mid = n/2;
	Person t(name.c_str(),0,"");
	if(a[mid]==t) return a+mid;
	if(t<a[mid]) return binarysearch(a,mid,name);
	return binarysearch(a+mid+1,n-(mid+1),name);
} */
Person* binarysearch(Person* a, int n, const string& name)
{
	int b=0, e=n-1;
	Person t(name.c_str(),0,"");
	while(b<=e){
		int mid = (b+e)/2;
		if(a[mid]==t) return a+mid;
		if(t<a[mid]) e = mid-1;
		else b = mid+1;
	}
	return NULL;
} 

int main()
{
	Person a[5]={
		Person("李霖",21,"新疆烏魯木齊"),
		Person("鍾玉龍",23,"大連"),
		Person("何軍軍",20,"重慶農村"),
		Person("蒲嗣良",16,"四川綿陽農村"),
		Person("王剛",18,"吉林通化")
	};
	for(int i=0; i<5; i++)
		for(int j=i+1; j<5; j++)
			if(a[j]<a[i])
				swap(a[j],a[i]);
	for(int i=0; i<5; i++)
		cout << a[i] << endl;
	string name;
	cout << "請輸入姓名:";
	cin >> name;
	Person* p = binarysearch(a,5,name);
	if(p!=NULL) cout << *p << endl;
	else cout << "找不到" << endl;
}