自定义结构或类的比较

 1 #include <iostream>
 2 #include <algorithm>
 3 using namespace std;
 4 struct act{
 5     int num;
 6     int s;
 7     int e;
 8 };
 9 bool lessact(const act& a1,const act &a2){
10     return a1.e<a2.e;
11 }
12 int main() {
13 
14     act *all=new act[n];
15 
16     sort(all.begin(),all.end(),lessact);
17 
18 }

 1 #include<iostream>
 2 #include<algorithm>
 3 #include <functional>
 4 using namespace std;
 5 
 6 struct Thing
 7 {
 8     int v;//单价
 9     int w;//重量
10     bool operator<(const Thing& other)const{
11         return v < other.v;
12     }
13     bool operator>(const Thing& other)const{
14         return v > other.v;
15     }
16 };
17 
18 ...
19     sort(t, t + n, greater<Thing>());
20 
21 ...

class SymbolLess : public std::binary_function<Symbol, Symbol, bool>{
public:  
    bool operator () (Symbol* lhs, Symbol* rhs) const  
    {  
        return lhs->getContent()< rhs->getContent();  
    }  
};  

...
set<Symbol*, SymbolLess> Symbols;//使用
...