Minimum of int array using recursion C++

Question

I'm trying to use recursion to find the minimum integer in an array.

This is my code:

int minArray(int* array, int size){
    if (size == 0){
        return array[0];
    }
    int min = array[0];
    if (min > minArray(array+1,size-1)){
        min = minArray(array+1,size-1);
    }
    return min;
}

What is wrong with it? If i call the function on {1,2,3,4,5}, it will return 0.

First thing that's wrong is that recursion is the wrong approach to this task... — keshlam
– keshlam, Commented May 3, 2016 at 3:00

MikeCAT · Accepted Answer · 2016-05-03 03:00:03Z

6

The condition is wrong. An array of zero elements has no elements, so accessing array[0] of it is illegal.

Also calling the function twice in this function should be avoided.

Try this:

int minArray(int* array, int size){
    if (size == 1){
        return array[0];
    }
    int min = array[0];
    int candidate = minArray(array+1,size-1);
    if (min > candidate){
        min = candidate;
    }
    return min;
}

answered May 3, 2016 at 3:00

MikeCAT

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3 Comments

R Sahu Over a year ago

@Danny, please note that the function is going to lead to UB if size is zero.

Bob Over a year ago

@RSahu so should i add if (size == 0) return 0; ?

R Sahu Over a year ago

@Danny, if you can, avoid calling the function if size is zero. When size is zero, how do you define minimum?

V.moreno · Accepted Answer · 2016-05-03 06:06:48Z

0

This solution is similar to the one of @MikeCat. I added the iterative version just for comparison purposes.

int min( int str[], int size)
{
  if (1==size)  // base case
  return str[0];
 else {
  int minor=min(&str[1],size-1); // each time the function is called its receives an array with an element less than the previous call.
  return str[0]<=minor ? str[0] : minor;
  }
}


// iterative approach. I have added the minor´s position indicator.
int mini(int str[], int size, int* position)
{
 int minor=str[0];
 for (int i=1;i<size;i++)
  if (str[i]<minor) {
   minor=str[i];
   *position=i;
   }
 return minor;
}

answered May 3, 2016 at 6:06

V.moreno

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