文章目录
一、基本概念
算法是STL中很重要的一部分，其功能包括比较，查找，排序，交换，遍历，复制等等。
最大的算法头文件是algorithm,封装了很多种模板类。还有numeric和functional也比较常见。
二、程序示例
1.遍历
#include<iostream>
#include<list>
#include<algorithm>
using namespace std;
void print(int a)
{
cout << a << " ";
}
class print1
{
public:
void operator()(int a)
{
cout << a << " ";
}
};
class print2
{
public:
int operator()(int a)
{
cout << a << " ";
return a;
}
};
void test()
{
list<int>L;
L.push_back(1);
L.push_back(2);
L.push_back(3);
//函数作为形参进行遍历输出
for_each(L.begin(), L.end(), print);
cout << endl;
//仿函数进行遍历
for_each(L.begin(), L.end(), print1());
cout << endl;
//transform实现遍历
list<int>L1;
L1.resize(L.size());
transform(L.begin(),L.end(),L1.begin(), print2());
}
int main()
{
test();
system("pause");
}
2. 查找
#include<iostream>
#include<list>
#include<algorithm>
using namespace std;
class Compare
{
public:
//一元谓词
bool operator()(int a)
{
return a > 1;
}
};
class Cat
{
public:
Cat(string name, int color, int age)
{
this->Name = name;
this->Color = color;
this->Age = age;
}
//自定义数据类型需要重载==
bool operator==(const Cat& cat)
{
if (Name == cat.Name && Color == cat.Color && Age == cat.Age)
{
return true;
}
else
{
return false;
}
}
public:
string Name;
int Color;
int Age;
};
class print1
{
public:
bool operator()(Cat& cat)
{
return cat.Age > 3;
}
};
void test()
{
list<int>L;
L.push_back(1);
L.push_back(2);
L.push_back(3);
//find算法查找
list<int>::iterator i = find(L.begin(), L.end(), 1);
if (i == L.end())
{
cout << "未查找到" << endl;
}
else
{
cout << "查找到" << *i<<endl;
}
//find_if查找
list<int>::iterator i1 = find_if(L.begin(),L.end(),Compare());
if (i1 == L.end())
{
cout << "未查找到" << endl;
}
else
{
cout << "查找到" << *i1 << endl;
}
//查找元素是否存在,无序序列结果未知
bool i2 = binary_search(L.begin(), L.end(), 1);
if (i2)
{
cout << "查找到1" << endl;
}
else
{
cout << "未查找到" << endl;
}
//count统计
int n = count(L.begin(), L.end(),1);
cout << n << endl;
//count_if统计
int n1 = count_if(L.begin(), L.end(), Compare());
cout << n1 << endl;
}
void test1()
{
list<Cat>L;
Cat cat1("小100", 76, 2);
Cat cat2("小200", 32, 2);
Cat cat3("小300", 32, 4);
Cat cat4("小400", 32, 3);
Cat cat5("小500", 54, 1);
//插入
L.push_back(cat1);
L.push_back(cat2);
L.push_back(cat3);
L.push_back(cat4);
L.push_back(cat5);
//find查找
list<Cat>::iterator i = find(L.begin(), L.end(), cat1);
if (i == L.end())
{
cout << "未查找到" << endl;
}
else
{
cout << "查找到" << (*i).Name << endl;
}
//find_if查找
list<Cat>::iterator i1 = find_if(L.begin(), L.end(), print1());
if (i1 == L.end())
{
cout << "未查找到" << endl;
}
else
{
cout << "查找到" << (*i1).Name << endl;
}
//查找相邻的重复元素
list<Cat>::iterator i2 = adjacent_find(L.begin(), L.end());
if (i2 == L.end())
{
cout << "未查找到" << endl;
}
else
{
cout << "查找到" << (*i2).Name << endl;
}
Cat cat6("小300", 32, 4);
//count统计，需要重载
int n = count(L.begin(), L.end(), cat6);
cout << n << endl;
}
int main()
{
test1();
system("pause");
}
3. 排序、拷贝、替换
#include<iostream>
#include<vector>
#include<algorithm>
#include<ctime>
using namespace std;
class Compare
{
public:
//一元谓词
bool operator()(int a,int b)
{
return a > b;
}
};
class Compare3
{
public:
//一元谓词
bool operator()(int a)
{
return a > 3;
}
};
void print(int a)
{
cout << a << " ";
}
class Cat
{
public:
Cat(string name, int color, int age)
{
this->Name = name;
this->Color = color;
this->Age = age;
}
//自定义数据类型需要重载==
bool operator==(const Cat& cat)
{
if (Name == cat.Name && Color == cat.Color && Age == cat.Age)
{
return true;
}
else
{
return false;
}
}
public:
string Name;
int Color;
int Age;
};
void test()
{
vector<int>L;
L.push_back(1);
L.push_back(2);
L.push_back(3);
L.push_back(4);
//降序
sort(L.begin(), L.end(),Compare());
for_each(L.begin(), L.end(), print);
cout << endl;
//greater<int>()
sort(L.begin(), L.end(),greater<int>());
for_each(L.begin(), L.end(), print);
cout << endl;
sort(L.begin(), L.end());
//随机打乱
//srand((unsigned int)time(NULL));
//random_shuffle(L.begin(), L.end());
//for_each(L.begin(), L.end(), print);
//cout << endl;
vector<int>L1(L);
vector<int>L2;
L2.resize(L.size()+L1.size());
//合并,默认只能同为升序的合并merge必须为有序序列
merge(L.begin(), L.end(), L1.begin(), L1.end(),L2.begin());
for_each(L2.begin(), L2.end(), print);
cout << endl;
//反转
reverse(L.begin(), L.end());
for_each(L.begin(), L.end(), print);
cout << endl;
//拷贝
vector<int>L3;
L3.resize(L.size());
copy(L.begin(), L.end(), L3.begin());
for_each(L3.begin(), L3.end(), print);
cout << endl;
//替换
replace(L.begin(), L.end(), 2, 5);
for_each(L.begin(), L.end(), print);
cout << endl;
replace_if(L.begin(), L.end(), Compare3(),20);
for_each(L.begin(), L.end(), print);
cout << endl;
//互换
swap(L, L1);
}
int main()
{
test();
system("pause");
}
4. numeric相关算法
#include<iostream>
#include<vector>
#include<numeric>
#include<algorithm>
#include<ctime>
using namespace std;
void print(int a)
{
cout << a << " ";
}
void test()
{
vector<int>L;
L.push_back(1);
L.push_back(2);
L.push_back(3);
L.push_back(4);
//计算容器元素的和，0为起始累加值
int total = accumulate(L.begin(), L.end(), 0);
cout << total<<endl;
//填充元素
vector<int>L1;
L1.resize(L.size());
fill(L1.begin(), L1.end(), 3);
for_each(L1.begin(), L1.end(), print);
cout << endl;
//求交集
vector<int>L2;
L2.resize(min(L.size(),L1.size()));
vector<int>::iterator i = set_intersection(L.begin(), L.end(), L1.begin(), L1.end(), L2.begin());
for_each(L2.begin(), i, print);
cout << endl;
//求并集
vector<int>L3;
L3.resize(L.size()+ L1.size());
vector<int>::iterator j = set_union(L.begin(), L.end(), L1.begin(), L1.end(), L3.begin());
for_each(L3.begin(), j, print);
cout << endl;
//差集
vector<int>L4;
L4.resize(max(L.size() , L1.size()));
vector<int>::iterator j1 = set_difference(L.begin(), L.end(), L1.begin(), L1.end(), L4.begin());
for_each(L4.begin(), j1, print);
}
int main()
{
test();
system("pause");
}
总结
以上只是stl算法中常见的，后续会随时补充新的算法。