遍历算法
for_each
for_each(v.begin(),v.end(),print01);
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//常用遍历算法 for_each
//普通函数
void print01(int val) {
cout << val << " ";
}
//仿函数
class print02 {
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(),print01);//起始迭代器，结束迭代器，函数名/仿函数对象
cout << endl;
for_each(v.begin(), v.end(), print02());
cout << endl;
}
int main() {
test01();
return 0;
}transform
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//遍历算法 transform 搬运容器到另一个容器中
class Transform {
public:
int operator()(int v) {
return v;
}
};
class MyPrint {
public:
void operator()(int val) {
cout << val << " ";
}
};
void test01() {
vector<int>v;
for (int i = 0; i < 10; i++)
v.push_back(i);
vector<int>vTarget;//目标容器
vTarget.resize(v.size());//目标容器需要提前开辟空间
transform(v.begin(), v.end(), vTarget.begin(), Transform());
for_each(vTarget.begin(), vTarget.end(), MyPrint());
cout << endl;
}
int main() {
test01();
return 0;
}查找算法
find
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
//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 << "未找到" << 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 == 让底层 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", 30);
Person p3("ccc", 40);
//放入到容器中
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
Person pp("bbb", 30);
vector<Person>::iterator it = find(v.begin(), v.end(), pp);//找和pp一样的
if (it == v.end()) {
cout << "未找到" << endl;
}
else {
cout << "找到了 姓名：" << it->m_Name << " 年龄：" << it->m_Age << endl;
}
}
int main() {
test01();
test02();
return 0;
}find_if 按条件查找
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
//find_if
//1.查找内置数据类型
class GreaterFive {//大于5的数
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 << "未找到" << endl;
}
else {
cout << "找到了>5的数据：" << *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 Greater25 {
public:
bool operator()(Person& p) {
return p.m_Age > 25;
}
};
void test02() {
vector<Person>v;
//创建数据
Person p1("tom", 27);
Person p2("mak", 25);
Person p3("san", 22);
Person p4("li", 23);
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
v.push_back(p4);
//找年龄>25的
vector<Person>::iterator it = find_if(v.begin(), v.end(), Greater25());
if (it == v.end()) {
cout << "未找到" << endl;
}
else {
cout << "找到了年龄>25的人 姓名：" << it->m_Name << endl;
}
}
int main() {
test01();
test02();
return 0;
}adjacent_find 查找相邻重复元素
cpp
#include<iostream>
using namespace std;
//adjacent_find 查找相邻重复元素
#include<vector>
#include<algorithm>
void test() {
vector<int>v;
v.push_back(5);
v.push_back(2);
v.push_back(4);
v.push_back(5);//相邻重复
v.push_back(5);
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 << "找到了：" << *pos << endl;//输出元素的值
}
}
int main() {
test();
return 0;
}binary_search 二分查找法 查找指定元素是否存在
cpp
#include<iostream>
using namespace std;
//binary_search 查找指定元素是否存在 条件：有序序列
#include<vector>
#include<algorithm>
void test() {
vector<int>v;
for (int i = 0; i < 10; i++)
{
v.push_back(i);
}
//查找元素中是否有9元素
bool ret = binary_search(v.begin(), v.end(), 9);
if (ret)
cout << "找到了" << endl;
else
cout << "未找到" << endl;
}
int main() {
test();
return 0;
}count 统计元素个数
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
//count
//1.统计内置数据类型
void test01() {
vector<int>v;
v.push_back(5);
v.push_back(2);
v.push_back(4);
v.push_back(5);
v.push_back(5);
int num = count(v.begin(),v.end(),5);//使用要包含算法的头文件
cout << 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;
}
//重载 == 让底层 count知道如何对比 person数据类型
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;//创建容器
Person p1("刘备", 23);//准备数据
Person p2("关于", 21);
Person p3("张飞", 26);
Person p4("赵云", 21);
//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);
Person p5("诸葛亮", 21);
int num = count(v.begin(), v.end(), p5);
cout << "和诸葛亮同岁的人员个数为：" << num << endl;
}
int main() {
test01();
cout << "--------------------------------" << endl;
test02();
return 0;
}count_if
按条件统计元素个数
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
//count_if
//1.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(20);
v.push_back(50);
v.push_back(30);
//统计>20的数
int num = count_if(v.begin(), v.end(), Greater20());//Pred 写一个谓词
cout << num << endl;//3
}
//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;
}
string m_Name;
int m_Age;
};
class AgeGreater20 {
public:
bool operator()(const Person& p) {
return p.m_Age > 21;
}
};
void test02() {
vector<Person>v;
Person p1("刘备", 23);//准备数据
Person p2("关于", 21);
Person p3("张飞", 26);
Person p4("赵云", 21);
//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);
//统计>21的数
int num = count_if(v.begin(), v.end(), AgeGreater20());
cout << num << endl;
}
int main() {
test01();
cout << "--------------------------------" << endl;
test02();
return 0;
}排序算法
sort
第三个参数可以不填，默认升序
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<functional>
void myPrint(int val) {
cout << val << " ";
}
void test01() {
vector<int>v;
v.push_back(1);
v.push_back(3);
v.push_back(5);
v.push_back(2);
v.push_back(4);
//sort升序
sort(v.begin(), v.end());
for_each(v.begin(), v.end(),myPrint);
cout << endl;
//sort降序
sort(v.begin(), v.end(),greater<int>());
for_each(v.begin(), v.end(), myPrint);
cout << endl;
}
int main() {
test01();
return 0;
}random_shuffle 洗牌 指定范围的元素随机调整次序
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//random_shuffle 洗牌 指定范围的元素随机调整次序
#include<ctime>//time的头文件
void myPrint(int val) {
cout << val << " ";
}
void test01() {
srand((unsigned int)time(NULL));//随机数
vector<int>v;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
v.push_back(5);
random_shuffle(v.begin(), v.end());
for_each(v.begin(), v.end(), myPrint);
}
int main() {
test01();
return 0;
}merge 合并两个有序容器
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//merge
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 + 1);
}
//目标容器
vector<int>vTarget;
//提前给目标容器分配空间
vTarget.resize(v1.size() + v2.size());
merge(v1.begin(), v1.end(), v2.begin(), v2.end(), vTarget.begin());
for_each(vTarget.begin(), vTarget.end(), myPrint);
cout << endl;
}
int main() {
test01();
return 0;
}reverse
拷贝和替换算法
copy
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//copy
void myPrint(int val) {
cout << val << " ";
}
void test01() {
vector<int>v1;
for (int i = 0; i < 10; i++)
v1.push_back(i);
vector<int>v2;
v2.resize(v1.size());
copy(v1.begin(), v1.end(), v2.begin());
for_each(v2.begin(), v2.end(), myPrint);
cout << endl;
}
int main() {
test01();
return 0;
}replace
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
class MyPrint {
public:
void operator()(int val) {
cout << val << " ";
}
};
void test01() {
vector<int>v;
v.push_back(1);
v.push_back(3);
v.push_back(3);
v.push_back(2);
v.push_back(3);
cout << "替换前" << endl;
for_each(v.begin(), v.end(), MyPrint());
cout << endl;
cout << "替换后" << endl;
replace(v.begin(), v.end(), 3, 3000);
for_each(v.begin(), v.end(), MyPrint());
cout << endl;
}
int main() {
test01();
return 0;
}replace_if
将区间内满足条件的元素替换成指定元素
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
class MyPrint {
public:
void operator()(int val) {
cout << val << " ";
}
};
class Greater3 {//谓词
public:
bool operator()(int val) {
return val >= 3;
}
};
void test01() {
vector<int>v;
v.push_back(1);
v.push_back(3);
v.push_back(3);
v.push_back(2);
v.push_back(4);
cout << "替换前" << endl;
for_each(v.begin(), v.end(), MyPrint());
cout << endl;
cout << "替换后" << endl;
replace_if(v.begin(), v.end(), Greater3(), 3000);//第三个位置 谓词
for_each(v.begin(), v.end(), MyPrint());
cout << endl;
}
int main() {
test01();
return 0;
}swap
互换两个同种类型的元素
cpp
swap(v1, v2);算术生成算法
accumulate
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<numeric>//accumulate头文件
void test() {
vector<int>v;
for (int i = 1; i <= 100; i++)
v.push_back(i);//5050
int total = accumulate(v.begin(), v.end(), 0);//起始累加值
cout << total << endl;
}
int main() {
test();
return 0;
}fill
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<numeric>//fill头文件
#include<algorithm>
void myPrint(int val) {
cout << val << " ";
}
void test() {
vector<int>v;
v.resize(5);//指定大小
//重新填充
fill(v.begin(), v.end(), 100);//100 100 100 100 100
for_each(v.begin(), v.end(), myPrint);
}
int main() {
test();
return 0;
}集合算法
前提是两个容器是有序的
交集
并集
差集
cpp
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//交集 set_intersection
//并集 set_union
void myPrint(int val) {
cout << val << " ";
}
void test() {
vector<int>v1;
vector<int>v2;
for (int i = 0; i < 10; i++) {
v1.push_back(i);//0~9
v2.push_back(i + 5);//5~14
}
//获取交集
vector<int>vTarget;
vTarget.resize(min(v1.size(),v2.size()));//最特殊情况 大容器包含小容器 两个中的较小值
vector<int>::iterator itEnd = set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), vTarget.begin());
for_each(vTarget.begin(), itEnd, myPrint);
cout << endl;
//获取并集
vector<int>v1Target;
v1Target.resize(v1.size()+v2.size());
vector<int>::iterator it = set_union(v1.begin(), v1.end(), v2.begin(), v2.end(), v1Target.begin());
for_each(v1Target.begin(), it, myPrint);
cout << endl;
//获取差集 v1和v2的
vector<int>v2Target;
v2Target.resize(max(v1.size(),v2.size()));
vector<int>::iterator itd = set_difference(v1.begin(), v1.end(), v2.begin(), v2.end(), v2Target.begin());
for_each(v2Target.begin(), itd, myPrint);
cout << endl;
}
int main() {
test();
return 0;
}