矩形覆盖

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); // 递归
        
        // 减少耗时
        int p = 2; 
        int pp = 1;
        int c = 0;
        for(int i=3; i<=target; i++){
            c = p+pp;
            pp = p;
            p = c;
        }
        return c;
    }
}