题解 | #跳台阶#

    //f(1) = 1 f(2) = 2 f{3) = 3
    //
    public int jumpFloor(int target) {
        
        return f(target);
    }
    public int f(int n){
        //公式 f(n) = f(n-1)+f(n-2)
        if(n <= 0){
            return 0;
        }
        if(n == 1){
            return 1;
        }
        if(n == 2){
            return 2;
        }
        int result = 0;
        int a = 1; //f(n-2)
        int b = 2; //f(n-1)
        for(int i = 3;i<=n;i++){
            result =  a + b;
            a = b;
            
            b = result;
        }
        
        return result;
    }
}