剑指offer - 斐波那契数列

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 arr[] = new int[n + 1];
        arr[0] = 0;
        arr[1] = 1;
        for (int i = 2; i <= n; i++) {
            arr[i] = arr[i - 1] + arr[i - 2];
        }
        return arr[n];
    }
}

public class Solution {
    public int Fibonacci(int n) {
        if (n <= 1) {
            return n;
        }
        //存储n位置值的变量
        int x = 1;
        //存储n-1位置的变量
        int y = 0;
        for (int i = 2; i <= n; i++) {
            //i位置的值
            x = x + y;
            //i-1位置的值
            y = x - y;
        }
        //返回n位置值
        return x;
    }
}