Recursive and non-recursive implementation of Fibonacci sequence in Java interview __java

Question: Find the nth number in the Fibonacci sequence.

The so-called Fibonacci sequence refers to: The first 2 numbers are 0 and 1. The number of i-1 and the number of i-2.

The first 10 numbers of the Fibonacci series are:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ...

Answer:

(i) Recursive implementation:

Class Solution {
    /**
     * @param n:an integer
     * @return an integer f (n) */public
    int Fibonacci (int n) {
       if (n==1) {return
           0;
       } else if (n==2) {return
           1;
       }
       else {return
           Fibonacci (n-1) +fibonacci (n-2);
}}} Total time consuming: 4634 ms

(ii) Non-recursive implementation

Class Solution {
    /**
     * @param n:an integer
     * @return an integer f (n) */public
    int Fibonacci (int n) {
        int before=0,behind=0;
        int result=0;
        for (int i=0;i<n;i++) {
            if (i==0) {
                result=0;
                before=0;
                behind=0;
            }
            else if (i==1) {
                result=1;
                before=0;
                Behind=result;
            } else{
                Result=before+behind;
                Before=behind;
                Behind=result
                
            }
        }
        return result;
    }
Total time consuming: 1389 ms

We see that the method of non recursion is obviously optimized and the time is reduced.