关注n,第n个中一个竖着覆盖,那么关注n-1,如果横着盖,则需要两个,关注n-2 n-1和n-2覆盖的和

public class Solution {
    public int rectCover(int target) {
        if(target == 0){
            return 0;
        }
        if(target == 1){
            return 1;
        }
        if(target == 2){
            return 2;
        }
        return rectCover(target-1)+rectCover(target-2);
    }
}