递推套路

跟跳台阶一样的解法，利用递推：

public class Solution {
    public int rectCover(int target) {
        if(target == 0)
            return 0;
        int a = 1, b = 1;
        for(int i = 1; i < target; i++){
            a = a + b;
            b = a - b;
        }
        return a;
    }
}