C++进阶STL-常用的拷贝和替换算法

悠悠 2022-05-06 01:26 133阅读 0赞

## copy ##

*  OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result)

例子：将v1的第二个元素开始到最后一个元素，拷贝给v2

#include "stdafx.h"
    #include <iostream>
    #include <algorithm>
    #include <vector>
    using namespace std;
    
    
    
    void Print(int n)
    { 
    	cout << " " << n;
    }
    int main()
    { 
    	vector<int> v1;
    	for (int i = 0; i < 5; i++)
    	{ 
    		v1.push_back(i);
    	}
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    
    	vector<int>v2;
    	v2.resize(v1.size()-1);
    
    	cout << "v2 : ";
    	copy(v1.begin()+1,v1.end(),v2.begin());
    	for_each(v2.begin(), v2.end(), Print); cout << endl;
    	
        return 0;
    }

![在这里插入图片描述][20181012151908123]

--------------------

## swap ##

*  void swap (T& a, T& b)

#include "stdafx.h"
    #include <iostream>
    #include <algorithm>
    #include <vector>
    #include <time.h>
    using namespace std;
    
    
    void Print(int n)
    { 
    	cout << " " << n;
    }
    int main()
    { 
    	srand((unsigned int) time(NULL));
    	vector<int> v1;
    	for (int i = 0; i < 5; i++)
    	{ 
    		v1.push_back(rand()%10);
    	}
    
    	vector<int>v2;
    	for (int i = 0; i < 4; i++)
    	{ 
    		v2.push_back(rand() % 10);
    	}
    
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    	cout << "v2 : ";
    	for_each(v2.begin(), v2.end(), Print); cout << endl;
    
    	swap(v1, v2);
    	cout << "----------------------------------------------------" << endl;//交换后
    
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    	cout << "v2 : ";
    	for_each(v2.begin(), v2.end(), Print); cout << endl;
        return 0;
    }

结果：  
![在这里插入图片描述][20181012153200794]

--------------------

## replace ##

*  void replace (ForwardIterator first, ForwardIterator last,  
    const T& old\_value, const T& new\_value)

#include "stdafx.h"
    #include <iostream>
    #include <algorithm>
    #include <vector>
    #include <time.h>
    using namespace std;
    
    
    void Print(int n)
    { 
    	cout << " " << n;
    }
    int main()
    { 
    	srand((unsigned int) time(NULL));
    	
    	vector<int> v1;
    	for (int i = 0; i < 10; i++)
    	{ 
    		v1.push_back(rand()%10);
    	}
    
    
    
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    
    	replace(v1.begin(),v1.end(), 0,100);
    	cout << "---------替换后----------" << endl;
    
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    
        return 0;
    }

结果：所有0，替换成100，如果没有0就不进行替换  
![在这里插入图片描述][20181012153638901]

--------------------

## replace\_if ##

*  void replace\_if (ForwardIterator first, ForwardIterator last,  
    UnaryPredicate pred, const T& new\_value)

#include "stdafx.h"
    #include <iostream>
    #include <algorithm>
    #include <vector>
    #include <time.h>
    using namespace std;
    
    
    void Print(int n)
    { 
    	cout << " " << n;
    }
     bool Compare(int n) 
    { 
    		return n > 5;
    }
    
    int main()
    { 
    	vector<int> v1;
    	for (int i = 0; i < 10; i++)
    	{ 
    		v1.push_back(i);
    	}
    
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    
    	replace_if(v1.begin(),v1.end(), Compare ,100); //如果Compare返回true 就替换成100
    	cout << "---------替换后----------" << endl;
    
    	cout << "v1 : ";
    	for_each(v1.begin(), v1.end(), Print); cout << endl;
    
        return 0;
    }

结果：  
![在这里插入图片描述][20181012154642551]

--------------------

[20181012151908123]: /images/20220506/af647e90734e43ac99d85e27669c6c98.png
[20181012153200794]: /images/20220506/cd953b3a5a7c4e809c2430529e3db1a9.png
[20181012153638901]: /images/20220506/c6a407d847b04ac48f45217e9a617938.png
[20181012154642551]: /images/20220506/fc8fdf47e4aa44de95910c67172c8424.png