Vector & find_if in C ++

<STL Application> vector & find_if

Someone asked a struct named C as follows:

code:
  struct C{   int v1;   int v2;};
  

It should be used to declare a vector as a vector <C> CV;

What should I do when I want to search for internal elements ??
The general solution is to use the for () loop to search for rows. In fact, such a straight picture is also simple.

This provides another solution for ease of use ....
Find_if () provides the find_if () statement, but it is a pity that only one statement can be written.
In addition, the operator inputs the type of * iterator, rather than the equivalent value.

For example, V1 and V2 of the objects in this CV are sequential
V1 v2
1 100
2 52
3 25
4 75
5 84
6 33

So what should we do if we look for an object with V2 = 75?
1. functor point

code:
  bool Cfind75(const C& obj){        return obj.v2==75;}
  

2. functor

code:
  class Cfind75{       public:          bool operator()(const C& obj)          {               return obj.v2==75;          }};
  

However, it would be worse than the limit value to be killed !!
No thanks... so this time the template will be used ....
So we have to change

code:
  template<int n>class CComp{    public:        bool operator()(const C& lhs)        {            return (lhs.v2==n);        }};
  

How to use it ?? Very simple ....

code:
  vector<C>::iterator cviter =         find_if(cv.begin(),cv.end(),CComp<75>());
  

Otherwise, cviter is the position where the V2 value of the C-type object in the original CV is 75.
--
I have no questions about small applications. However, those unfamiliar with STL are often ignored.

1. # Include <iostream>
2. # Include <algorithm>
3. # Include <vector>
4. # Include <cstdlib>
6. Using namespace STD;
8. Struct C
9. {
10. C (): V1 (0), V2 (0 ){}
11. C (const Int & val1, const Int & val2): V1 (val1), V2 (val2 ){}
12. C Operator () (const Int & val1, const Int & val2)
13. {
14. V1 = val1;
15. V2 = val2;
16. Return * this;
17. }
18. ~ C (){}
19. Int V1;
20. Int V2;
21. };
22. Template <int n>
23. Class ccomp {
24. Public:
25. Bool operator () (const C & LHS)
26. {
27. Return (LHS. v2 = N );
28. }
29. };
31. Int main (INT argc, char * argv [])
32. {
33. Vector <C> CV;
34. C val;
35. Cv. push_back (Val (1,100 ));
36. Cv. push_back (Val (2, 52 ));
37. Cv. push_back (Val (3,25 ));
38. Cv. push_back (Val (4, 75 ));
39. Cv. push_back (Val (5, 84 ));
40. Cv. push_back (Val (6, 33 ));
42. Vector <C >:: iterator cviter =
43. Find_if (cv. Begin (), cv. End (), ccomp <75> ());
44. Cout <cviter-> V1 <"" <cviter-> V2 <Endl;
45. Cout <Endl;
47. System ("pause ");
48. Return 0;
49. }