斐波那契 · 通项公式

通项公式解法：

public class Solution {
    public int JumpFloor(int target) {
        double k = 1.0/Math.sqrt(5);
        double a = (1.0 + Math.sqrt(5))/2.0;
        double b = (1.0 - Math.sqrt(5))/2.0;
        int n = target + 1;
        return (int)(k*(Math.pow(a, n) - Math.pow(b, n)));
    }
}