c++STL之常用查找算法
引入#include<algorithm>
算法简介：
- find：查找元素
- find_if：按条件查找
- adjacent_find：查找相邻房重复的元素
- binary_search：二分查找
- count：统计元素个数
- count_if：按条件统计元素个数
1.find
#include<iostream>
using namespace std;
#include <vector>
#include <algorithm>
#include <string>
//常用查找算法
//find
//查找 内置数据类型
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
//查找 容器中 是否有 5 这个元素
vector<int>::iterator it = find(v.begin(), v.end(), 5);
if (it == v.end())
{
cout << "没有找到！" << endl;
}
else
{
cout << "找到： " << *it << endl;
}
}
class Person
{
public:
Person(string name, int age)
{
this->m_Name = name;
this->m_Age = age;
}
//重载 == 底层find知道如何对比person数据类型
bool operator==( const Person & p)
{
if (this->m_Name == p.m_Name && this->m_Age == p.m_Age)
{
return true;
}
else
{
return false;
}
}
string m_Name;
int m_Age;
};
//查找 自定义数据类型
void test02()
{
vector<Person>v;
//创建数据
Person p1("aaa", 10);
Person p2("bbb", 20);
Person p3("ccc", 30);
Person p4("ddd", 40);
//放入到容器中
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
v.push_back(p4);
Person pp("bbb", 20);
vector<Person>::iterator it = find(v.begin(), v.end(), pp);
if (it == v.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到元素 姓名：" << it->m_Name << " 年龄： " << it->m_Age << endl;
}
}
int main() {
//test01();
test02();
system("pause");
return 0;
}2.find_if
#include<iostream>
using namespace std;
#include <vector>
#include <algorithm>
#include <string>
//常用查找算法 find_if
//1、查找内置数据类型
class GreaterFive
{
public:
bool operator()(int val)
{
return val > 5;
}
};
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());
if (it == v.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到大于5的数字为： " << *it << endl;
}
}
//2、查找自定义数据类型
class Person
{
public:
Person(string name, int age)
{
this->m_Name = name;
this->m_Age = age;
}
string m_Name;
int m_Age;
};
class Greater20
{
public:
bool operator()(Person &p)
{
return p.m_Age > 20;
}
};
void test02()
{
vector<Person>v;
//创建数据
Person p1("aaa", 10);
Person p2("bbb", 20);
Person p3("ccc", 30);
Person p4("ddd", 40);
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
v.push_back(p4);
//找年龄大于20的人
vector<Person>::iterator it = find_if(v.begin(), v.end(), Greater20());
if (it == v.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到姓名： " << it->m_Name << " 年龄： " << it->m_Age << endl;
}
}
int main() {
//test01();
test02();
system("pause");
return 0;
}3.adjacent_find
#include<iostream>
using namespace std;
#include <vector>
#include <algorithm>
//常用查找算法 adjacent_find
void test01()
{
vector<int>v;
v.push_back(0);
v.push_back(2);
v.push_back(0);
v.push_back(3);
v.push_back(1);
v.push_back(4);
v.push_back(3);
v.push_back(3);
vector<int>::iterator pos = adjacent_find(v.begin(), v.end());
if (pos == v.end())
{
cout << "未找到相邻重复元素" << endl;
}
else
{
cout << "找到相邻重复元素：" << *pos << endl;
}
}
int main() {
test01();
system("pause");
return 0;
}4.binary_search
#include<iostream>
using namespace std;
#include <vector>
#include <algorithm>
//常用查找算法 binary_search
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
//v.push_back(2); 如果是无序序列，结果未知！
//查找容器中是否有9 元素
//注意：容器必须是有序的序列
bool ret = binary_search(v.begin(), v.end(), 9);
if (ret)
{
cout << "找到了元素" << endl;
}
else
{
cout << "未找到" << endl;
}
}
int main() {
test01();
system("pause");
return 0;
}5.count
#include<iostream>
using namespace std;
#include <vector>
#include <algorithm>
#include <string>
//常用查找算法_count
//1、统计内置数据类型
void test01()
{
vector<int>v;
v.push_back(10);
v.push_back(40);
v.push_back(30);
v.push_back(40);
v.push_back(20);
v.push_back(40);
int num = count(v.begin(), v.end(), 40);
cout << "40的元素个数为： " << num << endl;
}
//2、统计自定义数据类型
class Person
{
public:
Person(string name, int age)
{
this->m_Name = name;
this->m_Age = age;
}
bool operator==(const Person & p)
{
if (this->m_Age == p.m_Age)
{
return true;
}
else
{
return false;
}
}
string m_Name;
int m_Age;
};
void test02()
{
vector<Person>v;
Person p1("刘备", 35);
Person p2("关羽", 35);
Person p3("张飞", 35);
Person p4("赵云", 30);
Person p5("曹操", 40);
//将人员插入到容器中
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
v.push_back(p4);
v.push_back(p5);
Person p("诸葛亮", 35);
int num = count(v.begin(), v.end(), p);
cout << "和诸葛亮同岁数的人员个数为：" << num << endl;
}
int main() {
//test01();
test02();
system("pause");
return 0;
}6.count_if
#include<iostream>
using namespace std;
#include <vector>
#include <algorithm>
//常用查找算法 count_if
//统计内置数据类型
class Greater20
{
public:
bool operator()(int val)
{
return val > 20;
}
};
void test01()
{
vector<int>v;
v.push_back(10);
v.push_back(40);
v.push_back(30);
v.push_back(20);
v.push_back(40);
v.push_back(20);
int num = count_if(v.begin(), v.end(), Greater20());
cout << "大于20的元素个数为： " << num << endl;
}
class Person
{
public:
Person(string name, int age)
{
this->m_Name = name;
this->m_Age = age;
}
string m_Name;
int m_Age;
};
class AgeGreater20
{
public:
bool operator()(const Person& p)
{
return p.m_Age > 20;
}
};
//统计自定义数据类型
void test02()
{
vector<Person>v;
Person p1("刘备", 35);
Person p2("关羽", 35);
Person p3("张飞", 35);
Person p4("赵云", 40);
Person p5("曹操", 20);
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
v.push_back(p4);
v.push_back(p5);
//统计 大于20岁人员个数
int num = count_if(v.begin(), v.end(), AgeGreater20());
cout << "大于20岁的人员个数为：" << num << endl;
}
int main() {
//test01();
test02();
system("pause");
return 0;
}举报
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