【剑指offer】斐波那契数列 --Java实现

public class Solution {
    public int Fibonacci(int n) {
        if(n <= 1) {
            return n;
        }
        return Fibonacci(n - 1) + Fibonacci(n - 2);         
    }
}

public class Solution {
    public int Fibonacci(int n) {
        if(n <= 1) {
            return n;
        }
        int[] a = new int[n + 1];
        a[0] = 0;
        a[1] = 1;
        for(int i = 2; i <= n; i++) {
            a[i] = a[i - 1] + a[i-2];
        }
        return a[n];
    }
}

public class Solution {
    public int Fibonacci(int n) {
        if(n <= 1) {
            return n;
        }
        int n1 = 0;
        int n2 = 1;
        int n3 = 0;
        for(int i = 2; i <= n; i++) {
            n3 = n1 + n2;
            n1 = n2;
            n2 = n3;
        }
        return n3;
    }
}

public class Solution {
    public int Fibonacci(int n) {
        if(n <= 1) {
            return n;
        }
        int n1 = 0;
        int n2 = 1;
        for(int i = 2; i <= n; i++) {
            n2 = n1 + n2;
            n1 = n2 - n1;
        }
        return n2;
    }
}