c++中STL容器中的排序

1.c++STL中只有list自带了排序函数：

（1）.若list中存放的是int类型或者string类型，直接利用sort即可：

list <int> list1;

          list1.sort();

         此时默认为升序，若要使用降序，直接自定义cmp函数即可。

（2）.若存放的是结构体或其他指针类型，需要自己定义比较结构体：

          struct student

{

int num;
};

          struct node

{

bool operator()(student a,student b)

return a.num>b.num;//从大到小排序
};

list<student> list1;

list1.sort(node());

 

 

2.vector排序：

使用algorithm中的sort函数：

#include<iostream>

#include<vector>

#include<algorithm>

using namespace std;

int cmp(int a,int b){

return a > b;//按降序排序

}

int main(){

vector<int> vec;

vec.push_back(324);

vec.push_back(344);

vec.push_back(2134);

vec.push_back(23);

vec.push_back(12);

vec.push_back(134);

vec.push_back(987);

sort(vec.begin(),vec.end(),cmp);

vector<int>::iterator it;

for(it = vec.begin();it != vec.end();it++)

cout<<*it<<" ";

cout<<endl;

return 0;

}

3.STL中的set排序：其中set本身是自带排序的，默认按升序进行排序:

#include <iostream>

#include <set>

using namespace std;

int main()

{

    set <int,less<int> > set1;//若使用less,则从小到大，若使用greater则从大到小。

    set1.insert(20);

    set1.insert(15);

    set1.insert(0);

    set1.insert(80);

    set<int>::iterator cset=set1.begin();

    while(cset!=set1.end())

    {

        cout<<*cset<<" ";

        cset++;

    }

    int m;

    cin>>m;

    return 0;

}

 

 

若定义set中存储的为结构体：

#include <iostream>

#include <string>

#include <set>

using namespace std;

struct intComp {

bool operator() (const int& lhs, const int& rhs) const{

return lhs > rhs;

}

};

struct strComp

{

bool operator() (const string& str1, const string& str2) const {

return str1.length() < str2.length();

}

};

int main() {

int a[] = {10, 20, 30, 40, 50};

set<int, intComp> s1(a, a + 5);

for (auto it = s1.cbegin(); it != s1.cend(); it++)

{

cout << *it << " ";

}

cout << endl;

string b[] = {"apple", "banana", "pear", "orange", "strawberry"};

set<string, strComp > s2(b, b + 5);

for (auto it = s2.cbegin(); it != s2.cend(); it++)

{

cout << *it << " ";

}

cout << endl;

system("pause");

return 0;

}

 

4.STL中map：

由于在map中是由红黑树实现的所以自带生序排序（key）

#include <iostream>

#include <map>

#include <string>

using namespace std;

int main()

{

map <int,string,less<int> > map1;//使用less有小到大 greater由大到小

map1[1]="HZ";

map1[8]="yu";

map1[100]="rue";

map1[-10]="23";

map<int,string>::iterator cmap=map1.begin();

while(cmap!=map1.end())

{

    cout<<cmap->first<<" ";

    cmap++;

}

int m;

cin>>m;

    return 0;

}

若存储的是结构体：

#include <iostream>

#include <map>

using namespace std;

struct student

{

int num;

};

bool operator <(student a,student b)

{

    return a.num>b.num;//由大到小

}

int main()

{

    map<student,int> map1;

    student a;

    a.num=100;

    map1[a]=10;

   

    student b;

    b.num=1000;

    map1[b]=11;

    student c;

    c.num=0;

    map1[c]=102;

    map<student,int> ::iterator st=map1.begin();

    while(st!=map1.end())

    {

        cout<<(st->first).num<<" ";

        st++;

    }

    int m;

    cin>>m;

    return 0;

}

map：（value）

#include <map>

#include <vector>

#include <algorithm>

#include <iostream>

using namespace std;

struct CmpByValue { 

  bool operator()(const pair<string,int> & lhs, const pair<string,int> & rhs)

  {return lhs.second > rhs.second;} 

};

void substrcount(string str)

{

    map<string,int> substr;

    string subs;

    for(int i =1; i<str.size();i++)

        for(int j =0; j<=str.size()-i;j++)

        {

subs = str.substr(j,i);

            if(substr.find(subs)==substr.end())

                substr[subs] = 1;

            else

                substr[subs] = substr[subs]+1;

        }

    vector<pair<string,int>> counts(substr.begin(),substr.end());

    sort(counts.begin(),counts.end(),CmpByValue());

    cout<<(counts.begin()->first)<<endl;

    cout<<counts.begin()->second<<endl;

}