Highest value of a vector, with recursion

Question

Highest value of a vector, with recursion

Navigation

#1 by (3 votes)

2

I'm studying about recursion and vectors, but I can not figure out how this method works, which returns the highest value using recursion.

int maximoR (int n, int v[]) {
   int x;
   if (n == 1) x = v[0];
   else {
      x = maximoR (n-1, v); 
      if (x < v[n-1]) x = v[n-1];
   }
   return x;
}

c array

asked by anonymous 05.09.2016 / 16:55

1 answer

Allow interactivity in UIScroolView and prevent interaction with content inside it as it scrolls Laravel - Return HTML or JSON in same Method

score 3 · Accepted Answer

First, this function would be called something like this:

int valores[] = {5, 10, 4, -4, 2, -7, 9};
int max = maximoR(7, valores); /* 7 = tamanho do vetor. */

Recursively, except when n is 1, it will always fall into else , creating a recursive call sequence like this (this is the process of going ):

maximoR(6, v);
maximoR(5, v);
maximoR(4, v);
maximoR(3, v);
maximoR(2, v);
maximoR(1, v);

At this point, the if will no longer drop to else and will return the v[0] element. Then, with each iteration it will start the process of back , where it will take the value of the previous iteration and it will compare with that of the n -th position of the array, always choosing the largest and returning this greater for the top call.

With this, here's what happens:

In the deepest iteration (the last one) it only returns the first value.
In the second, deepest iteration (the penultimate), it compares the second value with that obtained from the last iteration.
In the third, deepest iteration (the antepenultimate), it compares the third value with that obtained from the penultimate iteration.
...
In the first iteration (the shallowest), it compares the last value with that obtained from the second iteration.

So in the end the value chosen will be the largest element.