maximize a function with recursion c++

Question

I am trying to maximize this function in c++:

I have put this in the function:

int F(int n , int T ){

  if( T >= 0  &&  n == 0){

      return 0;

  }else if( T < 0){

      return INT_MIN;

  } else if(T >= 0  &&  n > 0){

      for(int i = 0 ; i <= m[n-1] ; i++){

       ganancia = max(i * v[n-1] + F(n-1,T-i*t[n-1]),ganancia );

      }

  }

}

but when I put on n 3 , T 8, t {1, 2, 2}, v {12, 15, 30} and finally on m{3, 3, 2} my program return 2, when it had to return 99.

In the picture there is an error, the h that is in the first comparison is a T. Sorry. — Quico Llinares Llorens, Mar 27 '16 at 11:08
There are 2 returns, one for the base case, when return 0, and another for the error case, that return INT_MIN. — Quico Llinares Llorens, Mar 27 '16 at 11:21
Ohh, you are saying that the assignment in the loop, should be a return ? — Quico Llinares Llorens, Mar 27 '16 at 11:27

score 1 · Accepted Answer · answered Mar 27 '16 at 11:09

1

You have three branches in the function, but only two return values. If you fail to return a value you will have undefined behavior. You need to return a value from all branches.

answered Mar 27 '16 at 11:09

Some programmer dude

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You mean, that I have to return something in the loop? – Quico Llinares Llorens Mar 27 '16 at 11:14
@QuicoLlinaresLlorens Not *in* the loop, but afterwards. – Some programmer dude Mar 27 '16 at 11:38
I have put a return after the loop, but the program now shows 81, instead of 13. – Quico Llinares Llorens Mar 27 '16 at 11:48
1

@QuicoLlinaresLlorens And you return a *value*, not just an empty `return` statement? Then you should step through the code in a debugger to help you find the problem. Also note that `int` is a signed type, so you need to think about what happens when `n` is less than zero, a case you don't handle now. – Some programmer dude Mar 27 '16 at 12:23

score 0 · Answer 2 · answered Mar 27 '16 at 11:35

Now I have my code like this:

int F(int n , int T ){

  if( T >= 0  &&  n == 0){

      return 0;

  }else if( T < 0){

      return INT_MIN;

  } else if(T >= 0  &&  n > 0){

      for(int i = 0 ; i <= m[n-1]-1 ; i++){

       return (max(i * v[n-1] + F(n-1,T-i*t[n-1]),(i+1) * v[n-1] + F(n-1,T- (i+1)*t[n-1]) ));

      }

  }

}

And now it is showing my program 12 instead of 13, at least I have left that 2 value. Thanks!

maximize a function with recursion c++

2 Answers2