"Algorithm" Fibonacci number

0007 Fibonacci number

Title Description

• We all know that Fibonacci number, and now asked to enter an integer n, you output the n-th Fibonacci number Fibonacci sequence of item (from 0, the first 0 is 0). n <= 39

Topics address

• https://www.nowcoder.com/practice/c6c7742f5ba7442aada113136ddea0c3

Report problem-solving

Based on recursive

This problem solution by the micro-channel public number 小猿刷题provided wrong, please correct me.

/**
 *  微信公众号"小猿刷题"
 */
public int Fibonacci(int N) {
    if(N == 0){
        return 0;
    }
    if(N == 1){
        return 1;
    }
    return Fibonacci(N-2) + Fibonacci(N-1);
}

Based on the array to achieve

This problem solution by the micro-channel public number 小猿刷题provided wrong, please correct me.

/**
 *  微信公众号"小猿刷题"
 */
public int Fibonacci(int N) {
    if(N == 0){
        return 0;
    }
    if(N == 1){
        return 1;
    }
    int [] arr = new int[N+1];
    arr[0] = 0;
    arr[1] = 1;
    for(int i = 2; i <= N; i++){
        arr[i] = arr[i-2] + arr[i-1];
    }
    return arr[N];
}

Based on exchange realized

This problem solution by the micro-channel public number 小猿刷题provided wrong, please correct me.

/**
 *  微信公众号"小猿刷题"
 */
public int Fibonacci(int N) {
    if(N == 0){
        return 0;
    }
    if(N == 1){
        return 1;
    }
    int a = 0;
    int b = 1;
    for(int i = 2; i <= N; i++){
        int sum = a + b;
        a = b;
        b = sum;
    }
    return b;
}