文章目录
- 第五章:
- 5.STL 常用算法
- 5.1 遍历算法
- 5.1.1 for_each
- 5.1.2 transform
- 5.2 查找算法
- 5.2.1 find
- 内置数据类型
- 自定义数据类型
- 5.2.2 find_if
- 内置数据类型
- 自定义数据类型
- 5.2.3 adjacent_find
- 5.2.4 binary_search
- 5.2.5 count
- 内置数据类型
- 自定义数据类型
- 5.2.6 count_if
- 内置数据类型
- 自定义数据类型
- 5.3 排序算法
- 5.3.1 sort
- 5.3.2 random_shuffle
- 5.3.3 merge
- 5.3.4 reverse
- 5.4 拷贝和替换算法
- 5.4.1 copy
- 5.4.2 replace
- 5.4.3 replace_if
- 5.4.4 swap
- 5.5 算术生成算法
- 5.5.1 accumulate
- 5.5.2 fill
- 5.6 集合算法
- 5.6.1 set_intersection
- 5.6.2 set_union
- 5.6.3 set_difference
第五章:
5.STL 常用算法
概述:
-
主要由algorithm functional numeric头文件组成
-
algortithm涉及到比较、交换、查找、遍历、复制等等
-
numeric体积很小,只包括几个在序列上进行简单的数学运算的模板函数
-
functional 定义了一些模板类,用于声明函数对象
5.1 遍历算法
-
for_each //遍历容器
-
transform //搬运容器到另一个容器中
5.1.1 for_each
函数原型:
-
for_each(iterator beg, iterator end, __func);
//_func 函数或者函数对象
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>//普通函数
void myPrint01(int val)
{cout << val << " ";
}//仿函数
class myPrint02
{
public:void operator()(int val){cout << val << " ";}
};void test01()
{vector<int>v;for (int i = 0; i < 10; i++){v.push_back(i);}for_each(v.begin(), v.end(), myPrint01);cout << endl;for_each(v.begin(), v.end(), myPrint02());cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.1.2 transform
函数原型:
- transform(iterator beg1, iterator end1, iterator beg2, _func);
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>class myTransform
{
public:int operator()(int val){return val;}
};//仿函数
class myPrint02
{
public:void operator()(int val){cout << val << " ";}
};void test01()
{vector<int>v;vector<int>aimT;for (int i = 0; i < 10; i++){v.push_back(i);}aimT.resize(v.size());transform(v.begin(), v.end(), aimT.begin(), myTransform());for_each(v.begin(), v.end(), myPrint02());cout << endl;for_each(aimT.begin(), aimT.end(), myPrint02());cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.2 查找算法
5.2.1 find
作用:查找指定元素,找到并返回指定元素的迭代器,找不到就返回结束迭代器end()
函数原型:
- find(iterator beg, iterator end, value);
内置数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>void test01()
{vector<int> v1;for (int i = 0; i < 10; i++){v1.push_back(i);}vector<int>::iterator it = find(v1.begin(), v1.end(), 5);if (it != v1.end()){cout << "找到元素" << *it << endl;}else{cout << "没有找到元素" << endl;}
}int main()
{test01();system("pause");return 0;
}
自定义数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>class Student
{
public:Student(string name, int age){this->m_Name = name;this->m_Age = age;}bool operator==(const Student& s) //重载=={if (this->m_Name == s.m_Name && this->m_Age == s.m_Age){return true;}else{return false;}}string m_Name;int m_Age;
};void test01()
{vector<Student> v2;Student s1("小明", 18);Student s2("小红", 19);Student s3("小王", 20);v2.push_back(s1);v2.push_back(s2);v2.push_back(s3);Student f("小明", 18);vector<Student>::iterator it = find(v2.begin(), v2.end(), f);if (it != v2.end()){cout << "找到元素" << " 姓名:" << it->m_Name << " 年龄:" << it->m_Age << endl;}else{cout << "没有找到元素" << endl;}
}int main()
{test01();system("pause");return 0;
}
5.2.2 find_if
作用:按条件查找元素
函数原型:
- find_if(iterator beg, iterator end, _Pred);
//_Pred 函数或谓词(返回bool类型的仿函数)
内置数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>class ExceedFour
{
public:bool operator()(int val){return val > 4;}
};void test01()
{vector<int> v1;for (int i = 0; i < 10; i++){v1.push_back(i);}vector<int>::iterator it = find_if(v1.begin(), v1.end(), ExceedFour());if (it != v1.end()){cout << "找到大于4的元素" << *it << endl;}else{cout << "没有找到元素" << endl;}
}int main()
{test01();system("pause");return 0;
}
自定义数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>class Student
{
public:Student(string name, int age){this->m_Name = name;this->m_Age = age;}string m_Name;int m_Age;
};class ExceedNineTeen{public:bool operator()(Student &s){return s.m_Age > 19;}};void test01()
{vector<Student> v2;Student s1("小明", 18);Student s2("小红", 19);Student s3("小王", 20);v2.push_back(s1);v2.push_back(s2);v2.push_back(s3);vector<Student>::iterator it = find_if(v2.begin(), v2.end(), ExceedNineTeen());if (it != v2.end()){cout << "找到元素" << " 姓名:" << it->m_Name << " 年龄:" << it->m_Age << endl;}else{cout << "没有找到元素" << endl;}
}int main()
{test01();system("pause");return 0;
}
5.2.3 adjacent_find
作用:查找相邻重复元素
函数原型:
- adjacent_find(iterator beg, iterator end);
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void test01()
{vector<int>v;v.push_back(10);v.push_back(20);v.push_back(30);v.push_back(40);v.push_back(40);v.push_back(50);vector<int>::iterator pos = adjacent_find(v.begin(), v.end());if (pos != v.end()){cout << "找到相邻重复元素:" << *pos << endl;}else{cout << "未找到" << endl;}}int main()
{test01();system("pause");return 0;
}
5.2.4 binary_search
作用:查找指定元素是否存在
函数原型:
- bool binary_search(iterator beg, iterator end);
注意:无序序列中无法使用
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void test01()
{vector<int>v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);bool ret = binary_search(v.begin(), v.end(), 4);if (ret){cout << "找到了" << endl;}else{cout << "没找到" << endl;}
}int main()
{test01();system("pause");return 0;
}
5.2.5 count
作用:统计元素个数
函数原型:
- count(iterator beg, iterator end, value);
内置数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>void test01()
{vector<int>v;v.push_back(10);v.push_back(20);v.push_back(30);v.push_back(40);v.push_back(40);int num = count(v.begin(), v.end(), 40);cout << "40的个数:" << num << endl;
}int main()
{test01();system("pause");return 0;
}
自定义数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>class Student
{
public:Student(string name, int age){this->m_Age = age;this->m_Name = name;}bool operator==(const Student& s){if (this->m_Age == s.m_Age){return true;}else{return false;}}string m_Name;int m_Age;
};void test01()
{vector<Student>v;Student s1("小明", 18);Student s2("小王", 22);Student s3("小红", 19);Student s4("小李", 19);Student s5("小黑", 20);Student sf("小茂", 19);v.push_back(s1);v.push_back(s2);v.push_back(s3);v.push_back(s4);v.push_back(s5);int num = count(v.begin(), v.end(), sf);cout << "与小茂同岁的个数:" << num << endl;
}int main()
{test01();system("pause");return 0;
}
5.2.6 count_if
作用:按条件统计元素个数
函数原型:
-
count_if(iterator beg, iterator end, _Pred)
//_Pred 谓词
内置数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>class ExceedThirty
{
public:bool operator()(int v){return v > 30;}
};void test01()
{vector<int>v;v.push_back(10);v.push_back(20);v.push_back(30);v.push_back(40);v.push_back(40);int num = count_if(v.begin(), v.end(), ExceedThirty());cout << "40的个数:" << num << endl;
}int main()
{test01();system("pause");return 0;
}
自定义数据类型
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>class Student
{
public:Student(string name, int age){this->m_Age = age;this->m_Name = name;}string m_Name;int m_Age;
};class ExceedNineTeen
{
public:bool operator()(const Student& s){return s.m_Age > 19;}
};void test01()
{vector<Student>v;Student s1("小明", 18);Student s2("小王", 22);Student s3("小红", 19);Student s4("小李", 19);Student s5("小黑", 20);v.push_back(s1);v.push_back(s2);v.push_back(s3);v.push_back(s4);v.push_back(s5);int num = count_if(v.begin(), v.end(), ExceedNineTeen());cout << "大于19岁的个数:" << num << endl;
}int main()
{test01();system("pause");return 0;
}
5.3 排序算法
-
sort
-
random_shuffle
-
merge
-
reverse
5.3.1 sort
作用:对容器中的元素进行排序
函数原型:
- sort(iterator beg, iterator end, _Pred);
//按值查找元素,找到返回指定位置迭代器,找不到返回结束迭代器位置
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v;v.push_back(10);v.push_back(40);v.push_back(60);v.push_back(20);v.push_back(50);v.push_back(30);//升序sort(v.begin(), v.end());for_each(v.begin(), v.end(), myPrint);cout << endl;//降序sort(v.begin(), v.end(), greater<int>());for_each(v.begin(), v.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.3.2 random_shuffle
作用:指定范围内的元素随机调整次序
该函数也被称为洗牌函数
函数原型:
- random_shuffle(iterator beg, iterator end);
#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>
#include <ctime>void myPrint(int val)
{cout << val << " ";
}void test01()
{srand((unsigned int)time(NULL));vector<int>v;for (int i = 0; i < 10; i++){v.push_back(i);}random_shuffle(v.begin(), v.end());for_each(v.begin(), v.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.3.3 merge
作用:两个容器元素合并存储到另一容器中
函数原型:
- merge(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest)
注意:两个容器必须是有序的
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;vector<int>v2;vector<int>aimV;for (int i = 0; i < 10; i++){v1.push_back(i);v2.push_back(i+3);}aimV.resize(v1.size() + v2.size());merge(v1.begin(), v1.end(), v2.begin(), v2.end(), aimV.begin());for_each(aimV.begin(), aimV.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.3.4 reverse
作用:将容器内元素进行反转
函数原型:
- reverse(iterator beg, iterator end);
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;for (int i = 0; i < 10; i++){v1.push_back(i);}cout << "反转前:" << endl;for_each(v1.begin(), v1.end(), myPrint);cout << endl;cout << "反转后:" << endl;reverse(v1.begin(), v1.end());for_each(v1.begin(), v1.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.4 拷贝和替换算法
-
copy
-
replace
-
replace_if
-
swap
5.4.1 copy
作用:容器内指定范围的元素拷贝到另一容器中
函数原型:
-
copy(iterator beg, iterator end, iterator dest);
//按值查找元素,找到返回指定位置迭代器,找不到返回结束迭代器位置
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>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.resize(v1.size());for_each(v1.begin(), v1.end(), myPrint);cout << endl;copy(v1.begin(), v1.end(), v2.begin());for_each(v2.begin(), v2.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.4.2 replace
作用:将容器内指定范围的原元素修改为新元素
函数原型:
- replace(iterator beg, iterator end, oldvalue, newvalue);
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;for (int i = 0; i < 10; i++){v1.push_back(i);}cout << "替换前:" << endl;for_each(v1.begin(), v1.end(), myPrint);cout << endl;cout << "替换后:" << endl;replace(v1.begin(), v1.end(), 2, 20);for_each(v1.begin(), v1.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.4.3 replace_if
作用:将区间内满足条件的元素,替换为指定元素
函数原型:
- replace_if(iterator beg, iterator end, _Pred, newvalue);
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}class ExceedEqualFour
{
public:bool operator()(int val){return val >= 4;}
};void test01()
{vector<int>v1;for (int i = 0; i < 10; i++){v1.push_back(i);}cout << "替换前:" << endl;for_each(v1.begin(), v1.end(), myPrint);cout << endl;cout << "替换后:" << endl;replace_if(v1.begin(), v1.end(), ExceedEqualFour(), 20); for_each(v1.begin(), v1.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.4.4 swap
作用:互换两个容器的元素
函数原型:
- swap(container c1, container c2);
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>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+10);}cout << "交换前:" << endl;for_each(v1.begin(), v1.end(), myPrint);cout << endl;for_each(v2.begin(), v2.end(), myPrint);cout << endl;cout << "交换后:" << endl;swap(v1, v2);for_each(v1.begin(), v1.end(), myPrint);cout << endl;for_each(v2.begin(), v2.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
{test01();system("pause");return 0;
}
5.5 算术生成算法
注意:算术生成算法属于小型算法,使用时需包含头文件numeric
-
accumulate
-
fill
5.5.1 accumulate
作用:计算区间内容器元素累计总和
函数原型:
-
accumulate(iterator beg, iterator end, value);
//value 起始值
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>
#include <numeric>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 = " << total << endl;
}int main()
{test01();system("pause");return 0;
}
5.5.2 fill
作用:向容器中填充指定元素
函数原型:
- fill(iterator beg, iterator end, value)
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>
#include <numeric>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;v1.resize(10);fill(v1.begin(), v1.end(), 10);for_each(v1.begin(), v1.end(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
d(), myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}
5.6 集合算法
-
set_intersection
-
set_union
-
set_difference
5.6.1 set_intersection
作用:求两个集合的交集
函数原型:
- set_intersection(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
//dest 目标容器开始迭代器
注意:两个集合必须是有序序列
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;vector<int>v2;vector<int>aimT;for (int i = 0; i < 10; i++){v1.push_back(i);v2.push_back(i + 3);}aimT.resize(min(v1.size(), v2.size()));cout << "v1和v2的交集为:" << endl;vector<int>::iterator itEnd = set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), aimT.begin());for_each(aimT.begin(), itEnd, myPrint);cout << endl;}int main()
{test01();system("pause");return 0;
}
5.6.2 set_union
作用:求两个集合的并集
函数原型:
- set_union(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
//dest 目标容器开始迭代器
注意:两个集合必须是有序序列
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;vector<int>v2;vector<int>aimT;for (int i = 0; i < 10; i++){v1.push_back(i);v2.push_back(i + 3);}aimT.resize(v1.size()+ v2.size());cout << "v1和v2的并集为:" << endl;vector<int>::iterator itEnd = set_union(v1.begin(), v1.end(), v2.begin(), v2.end(), aimT.begin());for_each(aimT.begin(), itEnd, myPrint);cout << endl;}int main()
{test01();system("pause");return 0;
}
5.6.3 set_difference
作用:求两个集合的差集
函数原型:
- set_difference(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);
//dest 目标容器开始迭代器
注意:两个集合必须是有序序列,返回值是差集中最后一个元素的位置
#include <iostream>
using namespace std;
#include <algorithm>
#include <vector>void myPrint(int val)
{cout << val << " ";
}void test01()
{vector<int>v1;vector<int>v2;vector<int>aimT;for (int i = 0; i < 10; i++){v1.push_back(i);v2.push_back(i + 3);}aimT.resize(max(v1.size(), v2.size()));cout << "v1和v2的差集为:" << endl;vector<int>::iterator itEnd = set_difference(v1.begin(), v1.end(), v2.begin(), v2.end(), aimT.begin());for_each(aimT.begin(), itEnd, myPrint);cout << endl;cout << "v2和v1的差集为:" << endl;itEnd = set_difference(v2.begin(), v2.end(), v1.begin(), v1.end(), aimT.begin());for_each(aimT.begin(), itEnd, myPrint);cout << endl;
}int main()
{test01();system("pause");return 0;
}