for_each
#include <iostream>
#include<string>
#include<algorithm>
#include <list>
using namespace std;
template<class T>
void show(const T& val) {
cout <<"value="<< val << endl;
}
template<class T>
class Myprint {
public:
void operator()(const T& val) {
cout <<"value="<< val << endl;
}
};
template<class T,class T2>
void my_for_each(const T first, const T last, T2 show) {
for (auto it=first; it != last; it++)
{
show(*it);
}
}
int main() {
list<string> ls = {"aa","bb","cc","dd","ee","ff"};
my_for_each(ls.begin(), ls.end(),show<string>);
Myprint<string> myPrint;
my_for_each(ls.begin(), ls.end(),myPrint);
return 0;
}
std::find
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
int id;
string name;
bool operator==(const C1 c) {
return c.id == this->id && c.name == this->name;
}
};
void fun() {
vector<int>v1{1,22,33,4,5};
auto rs1 = find(v1.begin(),v1.end(), 33);
if (rs1 == v1.end())
{
cout << "没找到.."<<endl;
} else {
cout <<*rs1<<endl;
}
vector<C1>v2{C1(123,"tom"),C1(345, "jerry")};
auto rs2 = find(v2.begin(),v2.end(), C1(345, "jerry"));
if (rs2 == v2.end())
{
cout << "没找到.."<<endl;
} else {
cout <<(*rs2).id<<"---"<<(*rs2).name<<endl;
}
}
std::find_if
#include <iostream>
#include<string>
#include<algorithm>
#include <list>
using namespace std;
template<class T, class T2>
class Myprint {
public:
T2 m_val;
bool operator()(const T& val) {
if (val == m_val)
{
return true;
}
return false;
}
};
template<class T,class T2>
T myfind_if(const T first, const T last, T2 show) {
for (auto it=first; it != last; it++)
{
if (show(*it) == true)
{
return it;
}
return last;
}
}
int main() {
list<string> ls = {"ada","bb","cc","dd","ee","ff"};
Myprint<string,string> myPrint;
myPrint.m_val = "aa";
auto it2 = myfind_if(ls.begin(), ls.end(),myPrint);
if (it2 == ls.end())
{
cout <<"查找失败"<<endl;
} else {
cout <<"查找成功"<<endl;
}
return 0;
}
std::sort
#include <algorithm>
#include <functional>
#include <vector>
#include <iostream>
using namespace std;
int main()
{
vector<int> v = {9,5,2,6,7,0,4,1,3,8};
// 1. 默认升序排列
std::sort(v.begin(), v.end());
for (auto a : v) {
cout << a << " ";
}
cout << endl;
//2. 用标准库比较函数对象排序
std::sort(v.begin(), v.end(), std::greater<int>());
for (auto a : v) {
std::cout << a << " ";
}
cout << endl;
//3. 用 lambda 表达式排序
std::sort(v.begin(), v.end(), [](int a, int b) {
return b < a;
});
for (auto a : v) {
cout << a << " ";
}
cout << endl;
}
统计算法
#include <iostream>
#include<string>
#include <vector>
#include <algorithm>
using namespace std;
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
int id;
string name;
bool operator==(const C1 c) {
return c.id == this->id && c.name == this->name;
}
};
void fun() {
vector<int>v1{1,22,33,22,4,5};
int rs1 = count(v1.begin(),v1.end(), 22);
cout << rs1<<endl;
// 统计自定义数据类型
vector<C1>v2{C1(123,"tom"),C1(345, "jerry"),C1(345, "jerry")};
int rs2 = count(v2.begin(),v2.end(), C1(345, "jerry"));
cout << rs2<<endl;
}
struct myFind1 {
bool operator()(int a) {
return a == 22;
}
};
struct myFind2 :public unary_function<int,bool> {
bool operator()(int a) const{
return a == 22;
}
};
struct myFind3 {
bool operator()(const C1 &a) {
return a.id == 345 && a.name == "jerry";
}
};
void fun1() {
// 统计等于22的元素个数
vector<int>v1{1,22,22,22,33,4,5};
int rs1 = count_if(v1.begin(), v1.end(), myFind1());
cout << rs1<<endl;
// 统计不等于22的元素个数
int rs2 = count_if(v1.begin(), v1.end(), not1(myFind2()));
cout << rs2<<endl;
vector<C1>v2{C1(123,"tom"),C1(345, "jerry"),C1(345, "jerry")};
int rs3 = count_if(v2.begin(),v2.end(), myFind3());
cout << rs3<<endl;
}
合并算法
#include <iostream>
#include<string>
#include <vector>
#include <algorithm>
using namespace std;
void fun() {
vector<int>v1{1,2,3,4};
vector<int>v2{3,4,5,6};
vector<int>v3;
v3.resize(v1.size()+v2.size());
// merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v3.begin()); 默认升序合并
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v3.begin(), greater<int>());
for(auto start = v3.begin(); start!=v3.end(); start++) {
cout <<*start<<" ";
}
}
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
int id;
string name;
};
struct myCompare {
bool operator()(const C1 &a, const C1 &b) {
return a.id < b.id;
}
};
// 自定义类型合并
void fun2() {
vector<C1>v1{C1(1,"tom1"),C1(2, "tom2"),C1(3, "tom3"),C1(4, "tom4")};
vector<C1>v2{C1(3,"jerry3"),C1(4,"jerry4"),C1(5,"jerry5"),C1(6,"jerry6")};
vector<C1>v3;
v3.resize(v1.size()+v2.size());
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v3.begin(),myCompare());
for(auto start = v3.begin(); start!=v3.end(); start++) {
cout <<(*start).id<<" : "<<(*start).name<<" ";
}
}
int main() {
fun2();
return 0;
}
image.png
随机算法（洗牌算法）
#include <iostream>
#include<string>
#include <vector>
#include <sys/time.h>
#include <algorithm> // std::shuffle
#include <random> // std::default_random_engine
#include<chrono>
using namespace std;
struct myRand{
int operator()(int i) {
return rand()%i;
}
};
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
int id;
string name;
};
void fun() {
srand(((unsigned int)time(NULL)));//随机数种子
vector<int>v1{1,2,3,4,5,6};
random_shuffle(v1.begin(), v1.end(), myRand());
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
cout <<endl;
vector<C1>v2{C1(1,"11"),C1(2, "22"),C1(3, "33"),C1(4, "44"),C1(5, "55"),C1(6, "66")};
random_shuffle(v2.begin(), v2.end(), myRand());
for(auto start = v2.begin(); start!=v2.end(); start++) {
cout <<(*start).id<<" : "<<(*start).name<<" ";
}
}
void fun2() {
vector<int>v1{1,2,3,4,5,6};
random_device rd;
unsigned seed = chrono::system_clock::now().time_since_epoch().count();
shuffle(v1.begin(),v1.end(),default_random_engine(seed));
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
}
int main() {
fun2();
return 0;
}
排序算法
#include <iostream>
#include<string>
#include <vector>
#include <algorithm>
using namespace std;
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
int id;
string name;
};
struct mySort{
bool operator()(const C1 &a,const C1 &b) {
return a.id > b.id;
}
};
void fun2() {
vector<int>v1{12,21,33,41,15,26};
// sort(v1.begin(), v1.end()); // 默认升序排列
sort(v1.begin(), v1.end(), greater<int>()); // 降序排列
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
cout << endl;
// 自定义数据类型
vector<C1>v2{C1(1,"tom1"),C1(2, "tom2"),C1(3, "tom3"),C1(4, "tom4"),
C1(3,"jerry3"),C1(4,"jerry4"),C1(5,"jerry5"),C1(6,"jerry6")};
sort(v2.begin(), v2.end(),mySort()); // 降序排列
for(auto start = v2.begin(); start!=v2.end(); start++) {
cout <<(*start).id<<":"<<(*start).name<<" ";
}
}
int main() {
fun2();
return 0;
}
image.png
反转算法
void fun2() {
vector<int>v1{12,21,33,41,15,26};
reverse(v1.begin(), v1.end());
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
}
image.png
算数生成算法
#include <iostream>
#include<string>
#include <vector>
#include <algorithm>
#include<numeric>
using namespace std;
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
int id;
string name;
};
struct myPlus{
int operator()(int a, const C1 &b) {
return a+b.id;
}
};
void fun1() {
vector<int>v1{1,2,3};
// accumulate默认是加法
auto rs = accumulate(v1.begin(), v1.end(), 10); // 10+1+2+3
// auto rs = accumulate(v1.begin()+1, v1.end(), 10); // 10+2+3
cout <<"rs:"<<rs<<endl;
// 减法运算
auto rs1 = accumulate(v1.begin(), v1.end(), 10, minus<int>()); // 10-1-2-3
cout <<"rs1"<<rs1<<endl;
// 乘法运算
auto rs2 = accumulate(v1.begin(), v1.end(), 1, multiplies<int>()); // 1*1*2*3
cout <<"rs2:"<<rs2<<endl;
//自定义的数据类型
vector<C1>v2 = {
C1(1,"1"),
C1(2,"2"),
C1(3,"3"),
};
auto rs3 = accumulate(v2.begin(), v2.end(), 10, myPlus());
cout <<"rs3:"<<rs3<<endl;
}
int main() {
fun1();
return 0;
}
image.png
填充算法
void fun2() {
vector<int>v1(5); //空间代大小为5个
fill(v1.begin(), v1.end(), 100);
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
cout <<endl;
vector<C1>v2;
v2.resize(3);
fill(v2.begin(), v2.end(), C1(1,"11"));
for(auto start = v2.begin(); start!=v2.end(); start++) {
cout <<(*start).id<<" "<<(*start).name<<endl;
}
}
image.png
集合算法
源容器元素都必须是有序的，且排序规则要保持一致，目标容器使用前要分配空间
- 取交集
- 取并集
- 取差集
#include <iostream>
#include<string>
#include <vector>
#include <algorithm>
#include<numeric>
using namespace std;
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
int id;
string name;
};
struct myCompare{
bool operator()(const C1 &a, const C1 &b) {
return a.id < b.id;
}
};
void fun1() {
vector<int>v1{1,2,3,4,5};
vector<int>v2{4,5,6,7,8,9};
vector<int>v3;
v3.resize(min(v1.size(), v2.size()));// 取交集最大个数为v1和v2里较小的元素个数
set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
for(auto start = v3.begin(); start!=v3.end(); start++) {
cout <<*start<<" ";
}
cout <<endl;
//自定义对象
vector<C1>v4{C1(1,"1"),C1(2,"2"),C1(3,"3"),C1(4,"4"),C1(5,"5")};
vector<C1>v5{C1(4,"4"),C1(5,"5"),C1(6,"6"),C1(7,"7"),C1(8,"8")};
vector<C1>v6;
v6.resize(min(v4.size(), v5.size()));
set_intersection(v4.begin(), v4.end(), v5.begin(), v5.end(), v6.begin(),myCompare());
for(auto start = v6.begin(); start!=v6.end(); start++) {
cout <<(*start).id<<" "<<(*start).name<<endl;
}
}
int main() {
fun1();
return 0;
}
image.png
拷贝算法
copy只负责复制，不负责申请空间，所以复制前必须有足够的空间
#include <iostream>
#include<string>
#include <vector>
#include <algorithm>
using namespace std;
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
int id;
string name;
};
void fun2() {
vector<int>v1{12,21,33,41,15,26};
vector<int>v2;
v2.resize(v1.size());
std::copy(v1.begin(), v1.end(), v2.begin());
for(auto start = v2.begin(); start!=v2.end(); start++) {
cout <<*start<<" ";
}
cout << endl;
// 自定义数据类型
vector<C1>v3{C1(1,"1"),C1(2,"2"),C1(3,"3"),C1(4,"4"),C1(5,"5")};
vector<C1>v4;
v4.resize(v3.size());
std::copy(v3.begin(), v3.end(), v4.begin());
for(auto start = v4.begin(); start!=v4.end(); start++) {
cout <<(*start).id<<" "<<(*start).name<<endl;
}
}
int main() {
fun2();
return 0;
}
image.png
替换算法
#include <iostream>
#include<string>
#include <vector>
#include<functional>
#include <algorithm>
using namespace std;
class C1{
public:
C1(int id,string name) {
this->id = id;
this->name = name;
}
C1(){}
bool operator==(const C1 &a) {
return a.id == this->id && a.name == this->name;
}
int id;
string name;
};
// 将对应的值替换为指定的值
void fun1() {
vector<int>v1{12,21,33,41,33,26};
replace(v1.begin(), v1.end(), 33, 1000); // 替换v1中的33为100
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
cout << endl;
//自定义类型
vector<C1>v2{C1(1,"1"),C1(1,"1"),C1(3,"3"),C1(4,"4"),C1(5,"5")};
replace(v2.begin(), v2.end(), C1(1,"1"), C1(100, "100"));
for(auto start = v2.begin(); start!=v2.end(); start++) {
cout <<(*start).id<<" "<<(*start).name<<endl;
}
}
struct myCompare :public binary_function<int, int ,bool>{
bool operator()(int a, int b) const{
return a < b;
}
};
// 将满足条件的值替换为指定的值
void fun2() {
vector<int>v1{12,21,33,41,33,26};
replace_if(v1.begin(), v1.end(), bind2nd(myCompare(), 33), 1000);
for(auto start = v1.begin(); start!=v1.end(); start++) {
cout <<*start<<" ";
}
cout << endl;
}
int main() {
fun2();
return 0;
}
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