- 算法主要由头文件
<algorithm>
,<functional>
,<numeric>
组成 是所有STL头文件中最大的一个,范围涉及到比较、交换、查找、遍历、复制、删除等 体积很小,只包括几个在序列上面进行简单数学运算的模板函数 定义了一些模板类,用来声明函数对象
常用遍历算法
for_each遍历
for_each(iterator beg, iterator end, _func);
//遍历容器
beg
//起始迭代器end
//结束迭代器_func()
//函数或函数对象
for_each是实际开发中最常用的遍历算法,需要熟练掌握
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
//普通函数
void myPrint(int val)
{
cout << val << " ";
}
//仿函数
class myPrint2
{
public:
void operator()(int val)
{
cout << val << " ";
}
};
int main()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
for_each(v.begin(), v.end(), myPrint);
cout << endl;
for_each(v.begin(), v.end(), myPrint2());
return 0;
}
transform搬运
transform(iterator beg1, iterator end1, iterator beg2, _func);
//搬运容器
beg1
//源容器开始迭代器end1
//源容器结束迭代器beg2
//目标容器开始迭代器_func
//函数或函数对象
搬运的目标容器必须提前开辟空间,否则无法正常搬运
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
class Transform
{
public:
int operator()(int val)
{
return val;
}
};
int main()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
vector<int>v2;
v2.resize(v.size());
transform(v.begin(), v.end(), v2.begin(), Transform());
for (vector<int>::iterator it = v2.begin(); it != v2.end(); it++)
{
cout << *it << " ";
}
return 0;
}
常用查找算法
find
//查找元素find_if
//按条件查找元素adjacent_find
//查找相邻重复元素binary_search
//二分查找法count
//统计元素个数count_if
//按条件统计元素个数
find按值查找
find(iterator beg, iterator end, value);
//按值查找
beg
//开始迭代器end
//结束迭代器value
//查找的元素
返回一个迭代器,如果没有找到,返回end()
查找自定义数据类型需要重载==运算符,否则底层不知道如何对比
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
//查找内置数据类型
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
//返回一个迭代器,如果没有找到,返回end()
vector<int>::iterator it = find(v.begin(), v.end(), 5);
if (it == v.end())
cout << "没找到" << endl;
else
cout << "找到了" << *it << endl;
}
//查找自定义数据类型
class Person
{
public:
Person(string name,int age)
{
this->m_age = age;
this->m_name = name;
}
//重载==运算符,让find知道如何对比Person类型数据
bool operator==(const Person& p)
{
if (p.m_age == this->m_age && p.m_name == this->m_name)
return true;
else
return false;
}
string m_name;
int m_age;
};
void test02()
{
//准备数据
Person p1("A", 1);
Person p2("B", 2);
Person p3("C", 3);
Person p4("D", 4);
Person p5("E", 5);
//放入容器中
vector<Person>p;
p.push_back(p1);
p.push_back(p2);
p.push_back(p3);
p.push_back(p4);
p.push_back(p5);
//查找
Person p6("A", 1);
vector<Person>::iterator it = find(p.begin(), p.end(), p6);
//输出,验证结果
if (it == p.end())
cout << "没找到" << endl;
else
cout << "找到了" << it->m_name << it->m_age << endl;
}
int main()
{
test01();
test02();
return 0;
}
find_if条件查找
find_if(iterator beg, iterator end, _Pred);
beg
//开始迭代器end
//结束迭代器_Pred
//函数或者谓词(返回bool数据类型的仿函数)
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
//查找内置数据类型
class GreaterFive
{
public:
bool operator()(int v)
{
return v > 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 << "没找到" << endl;
else
cout << "找到了" << *it << endl;
}
//查找自定义数据类型
class Person
{
public:
Person(string name, int age)
{
this->m_age = age;
this->m_name = name;
}
string m_name;
int m_age;
};
class GreaterThree
{
public:
bool operator()(Person& p)
{
return p.m_age > 3;
}
};
void test02()
{
//准备数据
Person p1("A", 1);
Person p2("B", 2);
Person p3("C", 3);
Person p4("D", 4);
Person p5("E", 5);
//放入容器中
vector<Person>p;
p.push_back(p1);
p.push_back(p2);
p.push_back(p3);
p.push_back(p4);
p.push_back(p5);
//查找
vector<Person>::iterator it = find_if(p.begin(), p.end(), GreaterThree());
//输出,验证结果
if (it == p.end())
cout << "没找到" << endl;
else
cout << "找到了" << it->m_name << it->m_age << endl;
}
int main()
{
test01();
test02();
return 0;
}
adjacent_find查找相邻重复元素
如果查到,返回相邻重复元素的第一个位置的迭代器
adjacent_find(iterator beg, iterator end)
beg
//开始迭代器end
//结束迭代器
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
v.push_back(5);
vector<int>::iterator it=adjacent_find(v.begin(), v.end());
if (it == v.end())
cout << "未找到相邻重复元素" << endl;
else
cout << "找到了相邻重复元素" << *it << endl;
}
int main()
{
test01();
return 0;
}
binary_search二分查找
bool binary_search(iterator beg, iterator end, value);
- 查找指定的元素,查到返回true,否则返回false
- 注意:在无序列表中不可用,如果是无序序列,结果未知
beg
//开始迭代器end
//结束迭代器value
//查找的元素
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
cout << binary_search(v.begin(), v.end(), 5) << endl;
}
int main()
{
test01();
return 0;
}
count统计
对于统计自定义数据类型,需要重载==运算符
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
//统计内置数据类型
void test01()
{
vector<int>v;
v.push_back(10);
v.push_back(20);
v.push_back(10);
cout << count(v.begin(), v.end(), 10) << endl;
}
//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;
}
//需要重载==运算符
//底层要求加const
bool operator==(const Person& p)
{
if (this->m_name == p.m_name)
return true;
}
string m_name;
int m_age;
};
void test02()
{
Person p1("A", 1);
Person p2("B", 2);
Person p3("A", 3);
Person p4("A", 4);
vector<Person>p;
p.push_back(p1);
p.push_back(p2);
p.push_back(p3);
cout << "与p4同名的元素个数" << count(p.begin(), p.end(), p4) << endl;
}
int main()
{
test01();
test02();
return 0;
}
count_if条件统计
按条件统计元素出现次数
count_if(iterator beg, iterator end, _Pred);
beg
//开始迭代器end
//结束迭代器_Pred
//函数或者谓词(返回bool数据类型的仿函数)
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
//统计内置数据类型
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);
}
cout << count_if(v.begin(), v.end(), GreaterFive()) << endl;
}
//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;
}
string m_name;
int m_age;
};
class AgeGreaterTwo
{
public:
bool operator()(const Person& p)
{
return p.m_age > 2;
}
};
void test02()
{
Person p1("A", 1);
Person p2("B", 2);
Person p3("A", 3);
Person p4("A", 4);
vector<Person>p;
p.push_back(p1);
p.push_back(p2);
p.push_back(p3);
p.push_back(p4);
//统计年龄大于2的人数
cout << count_if(p.begin(), p.end(), AgeGreaterTwo()) << endl;
}
int main()
{
test01();
test02();
return 0;
}
常用排序算法
sort
//对容器内元素进行排序random_shuffle
//随机洗牌,将指定范围内的元素重新排序merge
//容器元素合并,并储存到另一个容器中reverse
//反转指定范围的元素
sort排序
sort(iterator beg, iterator end, _Pred)
//排序
beg
//开始迭代器end
//结束迭代器_Pred
//函数或者谓词,可填可不填,不填则默认升序排列
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
//默认升序
sort(v.begin(), v.end());
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " " ;
}
cout << endl;
//使用内建函数对象实现降序排列
sort(v.begin(), v.end(), greater<int>());
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " ";
}
}
int main()
{
test01();
return 0;
}
random_shuffle随机洗牌
random_shuffle(iterator beg, iterator end);
//随机洗牌
- 只需要提供开始迭代器和结束迭代器
srand((unsigned int)time(NULL));
可以设置系统时间为随机数种子
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
random_shuffle(v.begin(), v.end());
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " " ;
}
cout << endl;
}
int main()
{
test01();
return 0;
}
merge合并
merge(iterator beg1, iterator end1, iterator beg2, iterator end2, dest);
//将两个容器元素合并,并储存到另一个容器中
- 两个容器必须是有序的
beg1
//容器1开始迭代器end1
//容器1结束迭代器beg2
//容器2开始迭代器end2
//容器2结束迭代器dest
//目标容器开始迭代器
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void Print(int val)
{
cout << val << " ";
}
void test01()
{
vector<int>v1;
vector<int>v2;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
v2.push_back(i + 1);
}
//目标容器
vector<int>v3;
//目标容器需要提前开辟空间
v3.resize(v1.size() + v2.size());
merge(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
//合并后仍然是有序容器
for_each(v3.begin(), v3.end(), Print);
}
int main()
{
test01();
return 0;
}
reverse反转
reverse(iterator beg, iterator end);
//反转指定范围内的元素
beg
//起始迭代器end
//结束迭代器
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void Print(int val)
{
cout << val << " ";
}
void test01()
{
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
for_each(v1.begin(), v1.end(), Print);
cout << endl;
//反转
reverse(v1.begin(), v1.end());
for_each(v1.begin(), v1.end(), Print);
}
int main()
{
test01();
return 0;
}
常用拷贝和替换算法
copy
//容器内指定范围的元素拷贝到另一个容器中replace
//将容器内指定范围的旧元素修改为新元素replace_if
//容器内指定范围满足条件的元素替换为新元素swap
//互换两个容器的元素
copy拷贝
copy(iterator beg, iterator end, iterator dest);
//容器内指定范围的元素拷贝到另一个容器中
beg
//开始迭代器end
//结束迭代器dest
//目标容器的开始迭代器
用到的比较少,直接用赋值操作更简单
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void Print(int val)
{
cout << val << " ";
}
void test01()
{
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
vector<int>v2;
//v2要提前开辟空间
v2.resize(v1.size());
copy(v1.begin(), v1.end(), v2.begin());
for_each(v2.begin(), v2.end(), Print);
}
int main()
{
test01();
return 0;
}
replace替换
replace(iterator beg, iterator end, oldvalue, newvalue);
//将区间内的旧元素替换为新元素
beg
//起始迭代器end
//结束迭代器oldvalue
//旧元素newvalue
//新元素
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
class Print
{
public:
void operator()(int val)
{
cout << val << " ";
}
};
void test01()
{
vector<int>v1;
v1.push_back(1);
v1.push_back(2);
v1.push_back(1);
v1.push_back(3);
for_each(v1.begin(), v1.end(), Print());
cout << endl;
//替换
replace(v1.begin(), v1.end(), 1, 2);
for_each(v1.begin(), v1.end(), Print());
}
int main()
{
test01();
return 0;
}
replace_if条件替换
replace_if(iterator beg, iterator end, _Pred, newvalue);
//容器内指定范围满足条件的元素替换为新元素
beg
//开始迭代器end
//结束迭代器_Pred
//谓词newvalue
//替换的新元素
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
class Print
{
public:
void operator()(int val)
{
cout << val << " ";
}
};
class GreaterFive
{
public:
bool operator()(const int& val)
{
return val > 5;
}
};
void test01()
{
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
replace_if(v.begin(), v.end(), GreaterFive(), 0);
for_each(v.begin(), v.end(), Print());
}
int main()
{
test01();
return 0;
}
swap互换
swap(container c1, container c2);
//互换两个容器的元素
c1
容器1c2
容器2
注意必须是同种容器
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
class Print
{
public:
void operator()(int val)
{
cout << val << " ";
}
};
class GreaterFive
{
public:
bool operator()(const int& val)
{
return val > 5;
}
};
void test01()
{
vector<int>v1;
vector<int>v2;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
v2.push_back(i + 2);
}
//交换前
for_each(v1.begin(), v1.end(), Print());
for_each(v2.begin(), v2.end(), Print());
cout << endl;
//交换后
swap(v1, v2);
for_each(v1.begin(), v1.end(), Print());
for_each(v2.begin(), v2.end(), Print());
}
int main()
{
test01();
return 0;
}
常用算术生成算法
算术生成算法属于小型算法,使用时包含的头文件为
accumulate
//计算容器元素累计总和fill
//向容器中添加元素
accumulate累积
accumulate(iterator beg, iterator end, value);
//计算容器元素累计总和
- beg//起始迭代器
- end//结束迭代器
- value//起始值
#include<iostream>
#include<vector>
#include<numeric>
using namespace std;
void test01()
{
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
int total = accumulate(v1.begin(), v1.end(), 0);
cout << total << endl;
}
int main()
{
test01();
return 0;
}
fill填充
fill(iterator beg, iterator end, value);
//向容器中添加元素
beg
//起始迭代器end
//结束迭代器value
//填充的值
#include<iostream>
#include<vector>
#include<numeric>
using namespace std;
void test01()
{
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
for (vector<int>::iterator it = v1.begin(); it != v1.end(); it++)
{
cout << *it << " ";
}
cout << endl;
fill(v1.begin(), v1.end(), 0);
for (vector<int>::iterator it = v1.begin(); it != v1.end(); it++)
{
cout << *it << " ";
}
}
int main()
{
test01();
return 0;
}
常用集合容器
set_intersection
//求两个容器的交集set_union
//求两个容器的并集set_difference
//求两个容器的差集
set_intersection求交集
set_intersection(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
//求两个容器的交集
beg1
//容器1开始迭代器end1
//容器1结束迭代器beg2
//容器2开始迭代器end2
//容器2结束迭代器dest
//目标容器开始迭代器
注意事项:
- 返回值为迭代器,指向交集最后一个元素的下一个位置
- 求交集的两个集合必须为有序数列
- 目标容器开辟空间需要从两个容器中取小值
交集就是两个容器重复的元素
#include<iostream>
#include<vector>
#include<numeric>
#include<algorithm>
using namespace std;
void myPrint(int val)
{
cout << val << " ";
}
void test01()
{
vector<int>v1;
vector<int>v2;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
v2.push_back(i + 2);
}
for_each(v1.begin(), v1.end(), myPrint);
cout << endl;
for_each(v2.begin(), v2.end(), myPrint);
cout << endl;
//目标容器需要提前开辟空间,最特殊的情况,大容器包含小容器
vector<int>v3;
v3.resize(min(v1.size(), v2.size()));
//取交集
vector<int>::iterator itEnd = set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
for_each(v3.begin(), itEnd, myPrint);
cout << endl;
//如果不用返回的itEnd,会把0也给打印出来
for_each(v3.begin(), v3.end(), myPrint);
}
int main()
{
test01();
return 0;
}
set_union求并集
set_union(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
//求两个容器的并集
beg1
//容器1开始迭代器end1
//容器1结束迭代器beg2
//容器2开始迭代器end2
//容器2结束迭代器dest
//目标容器开始迭代器
注意事项:
- 返回值为迭代器,指向并集最后一个元素的下一个位置
- 求并集的两个集合必须为有序数列
- 目标容器开辟空间需要两个容器相加
#include<iostream>
#include<vector>
#include<numeric>
#include<algorithm>
using namespace std;
void myPrint(int val)
{
cout << val << " ";
}
void test01()
{
vector<int>v1;
vector<int>v2;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
v2.push_back(i + 2);
}
for_each(v1.begin(), v1.end(), myPrint);
cout << endl;
for_each(v2.begin(), v2.end(), myPrint);
cout << endl;
//目标容器需要提前开辟空间,最特殊的情况,两个容器没有交集
vector<int>v3;
v3.resize(v1.size() + v2.size());
//取并集
vector<int>::iterator itEnd = set_union(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
for_each(v3.begin(), itEnd, myPrint);
cout << endl;
//如果不用返回的itEnd,会把0也给打印出来
for_each(v3.begin(), v3.end(), myPrint);
}
int main()
{
test01();
return 0;
}
set_difference求差集
set_difference(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
//求两个容器的差集
beg1
//容器1开始迭代器end1
//容器1结束迭代器beg2
//容器2开始迭代器end2
//容器2结束迭代器dest
//目标容器开始迭代器
注意事项:
- 返回值为迭代器,指向并集最后一个元素的下一个位置
- 求并集的两个集合必须为有序数列
- 目标容器开辟空间需要从两个容器中取大值
#include<iostream>
#include<vector>
#include<numeric>
#include<algorithm>
using namespace std;
void myPrint(int val)
{
cout << val << " ";
}
void test01()
{
vector<int>v1;
vector<int>v2;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
v2.push_back(i + 2);
}
for_each(v1.begin(), v1.end(), myPrint);
cout << endl;
for_each(v2.begin(), v2.end(), myPrint);
cout << endl;
//目标容器需要提前开辟空间,最特殊的情况,大容器和小容器没有交集
//取两个容器中大的size作为目标容器开辟空间
vector<int>v3;
v3.resize(max(v1.size(),v2.size()));
//取并集
vector<int>::iterator itEnd = set_difference(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
for_each(v3.begin(), itEnd, myPrint);
cout << endl;
//如果不用返回的itEnd,会把0也给打印出来
for_each(v3.begin(), v3.end(), myPrint);
}
int main()
{
test01();
return 0;
}
标签:总结,end,迭代,iterator,STL,back,v1,算法,include
From: https://www.cnblogs.com/wushf/p/17112760.html